Booting issues and my adventure - last Dell I'll ever purchase.

Although it was purchased recently, you neglected to mention that the device is an old model.  It was released about 7 - 8 years ago and is considered end-of-life to requires warranty support through manufacturers.

When equipped a discrete graphics, the workstation may require 130w barrel tip AC adapter to keep it running and charging the battery.  Note that power delivery over thunderbolt was not widely used back then.  Don't be surprise if your USB-C charger is underpower and may not providing enough charging power.  You need to verify the power requirements and acquire a proper charger for it to work.  Here is the owner's manual for your system https://www.dell.com/support/manuals/en-us/precision-m5510-workstation/prec5510_pub/technical-specifications?guid=guid-2d9c1e4c-a0e9-446f-b7f1-8fc090e0249c&lang=en-us

Until you have a proper power adapter, you can then perform a hard reset, with AC power and battery are removed from system, press and hold power button for 30 seconds.  Connecting power and test again.  Due to its age, you may want to replace the CMOS battery, ML-1220.  Remember to make adjustments in BIOS settings to match with the hardware and usages.

I did not realize that giving the full model, with which a simple search would tell the age.  I did state that it was out of warranty as well.  Never have I had a manufacturer ignore when I contact them, as a third party repair shop, and described an issue just to have them go "warranty is out" because they want their customers to have a good experience. This brings return customers.  Its even an AI that could easily say live customer support is unavailable but here is an automated response. I have, for a long time now, suggested to my customers to purchase other brands as the experiences I have had as a repair tech and my customers have had as first party Dell customers has been below standard.  I decided, after about 16 years of suggesting otherwise, decided to purchase a dell to see if the experience is any better than it was in the past and if I could suggest Dell computers to my customers again. Sadly, the experience I've had, even as both a developer and a repair tech, has been way below the experience I've had with the other brands I've used. 

No, it has nothing to do with needing a stronger adapter.  I have repaired computers for almost 20 years now.   I know how adapters work.  There is no justification for denying a charger that is fully capable of charging the laptop because the manufacturer pretends that they arent good enough at producing products to stabilize the power entering the laptop.  Note: I am fully aware that it may not be pretending and that Dells developers and engineering team may truly be incapable of such a feat. 

There is big different of recently purchased.  With a new machine, the issue(s) would likely be factory defects and many DELL-Care agents (support) would initiated contacting customer (through private message or posting here), as obligated by warranty contract and Dell requires them to do so.  Community users just stay clear of those as not much we can do to help.

If the machine, device is an aging model, out of warranty, customer must initiate the contact to request assistance.  Depending on the query, you can find answers for many questions at Customer Care Wiki https://www.dell.com/community/en/conversations/customer-care/faq-customer-care/647f9a75f4ccf8a8dee1b9d3

If the machine is out of warranty and you are seeking help from Community users, just disclose the full machine description and its issues, someone may have the answer, resolution to assist you for free.

Since you are a computer tech and knowing how Dell charger works, I can only offer info about the forum resource which assist customer with contact info. 

You are entitle to your opinion but how businesses are conducted in reality may not be as you thought.  It's nothing new to learn about each company built their products with proprietorship.  It's understandable when you decided this is your last Dell's.

But, thinking how things should work and ignoring what could work may hinder your effort to resolve your current issue.  Just want to emphasis on my previous comment, Dell OEM chargers are allowed full capacity access while non-Dell products are limited by BIOS firmware.  Hence, the charger reading in BIOS is important and more accurate info than what the charger' specs says.  

"Attempt to update the bios as it's a critical update.. warning.. less than 10% battery and "no" AC adapter.  Cannot update bios.. Force the bios update."

In the future, you might want to consider not attempting to update the bios while on battery, especially on an older system and without a recognized ac adapter connected and with less than 10% battery charge remaining. That is something I might do in order intentionally to brick the system or cause some kind of critical error.