How should i inform myself? Where is it written that export won't work?
Guess you missed this warning when setting up your wallet to use P2SH-P2PK addresses:
It says pretty clearly that "Only Armory 0.96+ can spend from" those addresses... attempting to claim fork coins from "P2SH" addresses like MultiSigs, Electrum 2FA and other "script"-type addresses has never been a straightforward "one click" solution.