While you might well be correct,

http://www.flyertalk.com/forum/british-airways-executive-club/1694194-interlining-bags-separate-tickets.html

post #17 indicates that this is (relatively) a recent change..

The link that I posted earlier - don't recall seeing that on the MH website last year- but I might have just missed that page, though I do recall seeing the post on the mandatory self check in thingie earlier. Will be on MH again in a week odd, will try asking.