You got a tier bonus on RJ? That isn't on the table there - maybe this is a temporary bug?
IB has a 300 minimum too (but then I accept you did say mickey mouse

) but JL has no minimum at all.
I always thought this was due to the fact it cost the airlines something behind the scenes to award miles in another's program - ISTR EI used to be 500 but when it went and 'enhanced' all its products and commenced its race to the bottom I recall they dropped to 300 to reduce the cost of awarding miles on el cheapo tickets. Depends on what they're willing to stump up for I guess. Likewise the 25% earning on AA discount fares is because BA doesn't AAward AAdvantage members 100% on its discount fares either.