Taking a screenshot through the screen capture tool in BTT, area selection mode, has a tiny delay after letting go off the left click. Alternatively, what happens is that the system now takes into account the position of the mouse after letting go but before taking the screenshot.
This is not the case when using shift+cmd+4.
This usually doesn't matter, but it's very annoying if you're trying to screenshot an image from Amazon or something, an image from any gallery that has a zoom effect when you mouse over it. When you let do, the image "under" the selection area updates, and what you intended to screenshot is now displaced.
I think it started happening after updating to Sequoia.
Instructions to replicate it in the following link:
Position the mouse over the lemon in the bottle's label. Try to screenshot the loupe. I attach what it should look like (taken with the macOS shortcut), and what it looks like with BTT.
In this example the loupe moved to the top right corner where my selection area ended.