No but half of 625 is very easy math (half of 600 is 300, half of 25 is 12.5) and it makes doing everything else so much easier.
That and in practice, tiles aren't found in dimensions of 26.25 cm, but 20, 25 or 30 cm.
Calculations with those numbers are trivial to make, and when they aren't trivial those numbers are also easier to type on a calculator than fractions.
It's "easy math" if you're trained to think and calculate in that way. Never assume something is universally easy because it comes easy to yourself.
not a convincing argument. Same can be said for the other side