You got it in one and by doing some extra homework on here there are many savvy travellers who might help you get what you need. Be grateful you are not in any number of the truly awful FFP that are out there.

Airlines dont block off seats in the hope that someone might use miles to buy the seat, rewards seats are only offered on a first come first served basis on airlines, trains and boats so if you are thinking of expanding your travel plans and joining other programmes I suggest you also budget for a whole case load of anti disappointment pills.