As I read it ...
FCOM 3.03.18
- FLAPS 2 .... SELECT
. If the aircraft speed is signaficantly higher than S on glide slope or it doesnt decelerate EXTEND landing gear to slow it down.. USE of speedbrakes are not recommended.
This is the recommendation. If you are at flap 2, don't use the speed brake.
. When the speedbrakes are deployed extending FLAPS beyond FLAPS 1 may induce a slight roll movment, and in calm conditions a small lateral asymtry may remain untill controled....
... and this is the explanation - if you use speed brake at any time with more than flap 1, you have roll problems. This simply means flap 2 and speedbrake can be a problem - it doesn't matter which is selected first, as long as you don't have both together.