Basic VLT Test and Question

We are replacing two Dell switches from "stacking" with two Dell network switches configured in "VLT" instead. Some of the devices connecting to the switch will not be configured for link aggregation (ESXi hosts, and firewall which does not support LACP), and I want to better understand how the switches handle these connections.

I did a few simple tests on the new VLT switches but I can't really make sense of what is going on. If anyone can explain the below it would be much appreciated. I'm just trying to get a better general understanding of what to expect with different failure scenarios at this stage, particularly with devices not connected with LACP.

Here is what I found during my testing:  

1. I connected two devices (not configured for LACP) via a single link to the switches. Both of the devices were on separate VLANs, but with routing enabled. I found that when the devices were connected on opposite switches (e.g. device 1 on switch 1, and device 2 on switch 2). They were not able to communicate to one another. Is this expected? I expected the VLTi link to still allow comms to both?
2. I then configured one of the devices with LACP but only a single link. Again, I found that when the devices were connected on opposite switches (e.g. device 1 on switch 1, and device 2 on switch 2) they were not able to communicate.
3. I then configured them to be on the same VLAN. To my surprise I found that they were then able to communicate even when across opposite switches. Why would this work when they are on the same VLAN?

If this is all as expected, I also want to avoid a situation where devices can't talk to one another due to the links being active across separate switches -- is there a way to handle this?