Excellent point. I don't know the answer to that. The two concepts are related but different enough that it seems to me that they should be distinct, thinking in terms of math and science.
What I've found online doesn't seem reliable, because the context is so loose that either word works (maximal/maximum) in translation. We need an Italian physicist to answer this one, perhaps. Seems to me if you're testing a prototype, you'd want to know whether you'd reached the maximal distance or the maximum distance. The former has some wiggle-room, the latter, none.
Enrico Fermi probably would have wanted to know something similar when helping develop the atomic bomb.