I agree that this would be fair, but it seemingly not true. "SEA" disallows "SEAL" on the next turn (correct answer ALES,) but then you are suddenly allowed to use "SEALED" later - because of my assumption of the rule, I didn't get this stage until the clue. Same with "LEASE" and "LEADERS," which are both allowed to use "LEA."

So it seems as though the rule is, you must mix up the letters for the following answer, but further answers are fair game to reuse letter combinations (or, it is applied arbitrarily.) Neither are very intuitive IMO.

OK yeah, that does sound fine once you say it, but since the only stated rule is “one more letter”, I don’t think it’s obvious enough.