This is an incorrect way of looking at it. Microsoft was growing at approximately 10-15% headcount year over year prior to COVID. If they reverted to the approximate 2020 headcount that would mean an overall decline in growth in comparison to a situation where COVID did not exist.
And the answer is, "Calculate what would have happened without Covid, assuming previous growth patterns, and compare that to current headcount."
So they would revert to the 2020 headcount plus a guess as to non-covid influenced headcount. A reasonable guess there is "about the same amount on average as pre-Covid growth."
A company growing 10% per year would be around 7x larger 20 years later. There's a limit on how big companies can get.
Yes, there is. Read Coase's seminal paper, The Nature of the Firm. Companies function by replacing market mechanisms with bureaucratic administration. That finds its end when internal coordination or misallocation of resources incurs more cost than it saves in transaction costs.
Conglomerates therefore have a ceiling in size, and it's the reason why unwinding them generally increases market value for the sum of its individual companies (in finance parlance: "conglomerate discount"). It's also why the Soviet Union didn't run very well, and very large conglomerates are usually the consequence of political/economic arrangements.