Hi,
I often have a Bear window in a narrow sidebar (1/3 or ¼ of the screen) on my MacBook. When I paste an image into it, the image can’t be resized to be larger than the initial size. If I make the window bigger and paste again, the image appears larger, so it’s not about the pixels in the source.
Here’s an example of the same picture, pasted when the window was narrow, and then pasted again after making the window wider.