I have seen a very good companies product basically destroyed over many years of fixing things in the wrong place.
In opensource software there is almost never a reason to do this, and never without discussing the problem first.
That said, I have no problem with the sanity check that systemd is doing. They are not working around anything, they are just checking that what they are getting has a chance of being what they expect to get. They know the size of the object that they are getting, and so they only get that much data. fetching more would potentially cause other grief.