mbr2gpt inaccurate info on Dell website

That is accurate information.  If you review the methods Dell provided on that page, when the users perform step #8 from diskpart to clean the drives, it would erase all data on the drives. 

8.  Type clean and press Enter key.

Or, when users follow Windows Disk Management to initialize the drive and using the wizard to create New Simple Volume, it would format the drive and erase all data on the drive.

3.  Verify that the disk status is Online, else right-click and select Initialize disk.

5.  Once the disk has been initialized, right-click the unallocated space and click New Simple Volume and follow the steps to complete the process.

Therefore, the caution is accurate if users follow those methods.  All data would be erased.

This answer is from a Dell Community contributor, not from Dell employee.

A blanket statement is made: Caution: Converting a disk drive from MBR to GPT or conversely erases all data from the drive.

Certainly all existing data will be lost using if diskpart or Disk Management methods are used but the data will not be lost if MBR2GPT.exe is used so the blanket statement is wrong and should have been qualified.

I'm guessing the same information could be understood differently depending how we read it.

The way I see it, that warning statement was made toward the instructions to convert a disk from MBR to GPT in that article.  That warning was accurate for the methods Dell prescribed in that article.

You only focus on the method of using MBR2GPT without modifying or delete data on the disk, that method was not prescribed in the article but it was mentioned.  If scroll down on that page, you will find a header mentioning MBR2GPT.exe with a link to Microsoft.  The warning statement did not cover MBR2GPT because Dell did not provide users any instructions for MBR2GPT.exe  

Convert MBR to GPT using MBR2GPT.exe

For instructions, please refer to the following Microsoft documents.  Convert MBR partition to GPT