You're fortunate that this is the first time you're hearing it, but it's been a business term for quite some time now. I've only ever heard it used as a euphemism for downsizing but one HR lady insisted the term was general, that if you were understaffed you'd still need to right size.

I asked her if in meetings that might lead to some confusion, and she was confident that it never would. She was also an idiot.

When I started getting mentioned in meetings for doing a really good job on tasks that she was supposed to be doing she fired me. She was fired just a few weeks later. Sorry, she was right sized.