No. The needed bandwidth is related to symbol rate. Normally it is 35-40% more than the symbol rate.
With Astra it is a legacy of the analogue band plan isn't it?
i.e. the analogue broadcasts on Astra 1A to 1D had 26MHz of Bandwidth needing 16 transponders for 250MHz.
Along comes Astra 1E/1F and they decided to use 20 transponders to cover 400MHz spectrum so these are 33MHz wide (if these had been used for analogue TV it would have been rather wasteful).
Then as Sky turns off it's analogue transmissions digital services start in the old analogue bands, but squeezed between the analogue channels and on the same craft so forcing a slightly less efficient use on those bands. With the G band being the same size as the analogue bands it looks like they kept the 26MHz bandwidth there too.
For whatever reason SES Astra like consistency (i.e. the same transponders in use at three different orbital positions - 19,2'E; 23,5'E and 28,2'E) so while 28,2'E wasn't used for analogue television it's ended up following the same plan as 19,2'E.