It does sound like that come to think of it.
It's the E190SR cause BA wanted a 'Short Runway' version. Embraer had three E190 versions; STD, LR and AR. And now thus the SR, specifically adapted to operate out of LCY. (or other short runways) Plus it's only got <100 seats, much less than the certified 114 seats.
The scope clause in a nutsthell is BA preventing anyone from flying an aircraft with >100 seats unless they are operated by BA mainline. The RJ100's were excempt from the scope clause but it meant that any new aircraft for BACF had to be less than 100 seats. There's more to it but this is why the E190 has got <100 seats.