You should look at what Jeff said, this certainly seems to target what you are seeing.
The default state for Windows you create using the IDE is implicit instance, at least it used to be (and I think it still is). If this is new to you (as it was to me many years ago), the rest of Jeff’s response maybe obscure because you do not really know what “implicit instance” means.
I suggest the following reads to get you familiar with it; and then maybe the rest of Jeff’s answer will sink in. If you already understand it then my apologies and ignore the rest.
Windows — Xojo documentation
implicit instance off - Getting Started - Xojo Programming Forum
Where is desktopWindow.implicitInstance - General - Xojo Programming Forum
Why implicit instance isnt your friend – Writings from the sticks (great-white-software.com)
I also thought there was a good Xojo blog on this topic but I did not find it via the good’ol google.