A long time ago the UK CAA would apply an aircraft weight retriction to commercial FIXED WING operations, once the aircraft got above a certain basic weight you could only fly one type, so you couldn't fly a B707 today and be rostered onto a DC9 tomorrow, then back to the 707 etc. Didn't stop you having the ratings on your licence though. No idea if the CAA apply such a rule to, say, the S61 and the civil Chinook?
Maybe Nepal has confused themselves with some other countries rules and applied it to helicopters?