Hi Ben, thanks for the support! I've questioned this myself and here are my thoughts: more often than not, as the number of staff increase, the business requires more equipment and potentially land to house the staff. Standard PPE analysis should still apply.

With work from home being a thing now, we're probably likely see PPE remain stable or even drop for services companies.

I guess the next thing to look at is the employee expenses on the expense statement. After deducting managment options, if the employee expenses are increasing significantly, you can expect that there's a growth in staff. At this point, you want to look at the operating profit margins. If employee expenses increase, yet profits are falling, then you can take a good guess that the growth was good for nothing.
My advice here is don't believe in management when they say that can invest to grow marketshare and cut cost later. It's really difficult to maintain a good margin while cutting costs. Instead, look for businesses that can raise their prices and people will continue using the service.

I hope I've answer your question. Thanks for asking as well!