I'm surprised it's not there, but I won't lose any sleep over it.
a) I did not use it very often. Once in a while, but not very often. I'm speaking only for myself.
b) As already mentioned, there is a "preview mode" that is very nearly full-screen. What are you not getting in that mode that you get in full-screen mode?
c) I like the handy-dandy "Current Frame Preview (F10)" button that produces a single frame at your project's resolution.
Bottom line for me... same as the first line of this post.
iClone 7... Character Creator... Substance Designer/Painter... Blender... Audacity...
Desktop (homebuilt) - Windows 10, Ryzen 9 3900x CPU, GTX 1080 GPU (8GB), 32GB RAM, Asus X570 Pro motherboard, 2TB SSD, terabytes of disk space, dual monitors.
Laptop - Windows 10, MSI GS63VR STEALTH-252, 16GB RAM, GTX 1060 (6GB), 256GB SSD and 1TB HDD