Disk Cleanup option

Every now and again, I run the built-in Disk Cleanup
program to get rid of cruft - much left behind by updates.
I did so the other day and there was an element in the
list of items to erase that I hadn't seen before. (It was
unchecked by default.) cleanup was offering to compress
the OS drive and produced an estimate of how much space
that would save. I'd never seen that before. Is it the
result of an update? (...or is MS planning to expand the
already bloated Windows system and is softening up the
blow to its customers in advance of using all their disk
space...)