Good news -- problem solved, not a 7+ Taskbar Tweaker issue!

TL;DR this Microsoft answer details how to turn off the "Make app icons on the taskbar easier to touch" option when not using tablet mode.  In short: search "Tablet mode settings" > Change additional tablet settings > Make app icons on the taskbar easier to touch.

Thanks for the explanation -- clever trick!  I found on my Surface Book 2, when hovering with a pending pin, the gap was wider than the compressed icon when using the option to reduce the gap in the 7+ Tasker Tweaker.  With the gap reduction option turned off, the hovering pending pin took the same width as a standard icon.  This was repeatable on my P52s, as well as when the Surface Book 2 was detached (making it even wider).  Regardless, the icon spacing in my docked Surface and my P52s look to be correctly gap-reduced as I remember from the past.

Below are the screenshots taken from my Surface Book 2 with a hovering pending pin and then with the item pinned.

In running through your exercise, I noticed other things were also increased in spacing.  In particular, just about everything in Windows explorer had increased spacing.  This lead me to search and find that Microsoft added and/or turned on the option to increase spacing in this latest update.  I must have missed that in their release notes /sarcasm.

Thanks again for all the help!  I am really glad to see you still keeping this tool alive and always immediately responding to updates.  I think I'm now due for another donation ;)

I suspect you are correct.  Unfortunately I do not have another way to reproduce.