That is good clarifying point. I meant for US contestants flying FAI contests outside the US, particularly Europe. I have zero expectation that the "jury" will mandate the use of only Estes and AT motors at all FAI contests.Actually, they don't.
Sure 10mm motors are cool, but note that the recent World Championships held here in the US were contested using only Estes and Aerotech motors. Will that carry over to the next Championships? The jury is still out on that, but the competitors seemed to appreciate the simplicity of using the same motors that were available to every other competitor.