it is not just that
there is also the chance that the scans will return too many false positives, it was all rushed so people could grab headlines.
The road to hell paved with good intention.
The problem as always is money and the users.
What this scan will actually achieve is probably quite minimal, the example given was someone with thousands of machines having to work out if they are infected or not, well you don't need a scanner for that.
i. You are running windows so you are obviously clueless and just assume you probably are penetrated, at least feel the fear.
ii. You haven't patched a windows box for yonks, those will be compromised.
iii. If you cannot be arsed to write your own scanner for the thousands of machines under your control please leave IT there is no place for you, you are a twat dangler.
iv. The paranoid ones who do patch but run windows, oh there will be a few, you are probably not compromised but get the wrong scanner or hey even get the right one, and you maybe compromised or in false positive land.
The above could have been written in 'I heart the system jerk speak', and should have been, so people realised what a futile attempt the scan would be. But, at heart most 'security guys' want to be crackers, there is no getting away from that, and if you think like a cracker then your security solutions won't work as security solutions, they will work as a crack.