Many rescues who have bonded rabbits do not separate them if the female is being neutered, there is no research to show that this is necessary. From our own research with hundreds of rabbits we have found that keeping rabbits with their partners if they are to visit the vets for any treatment or operation results in a quicker less stressful recovery. Likewise with humans if they are separated for days on end from their nearest and dearest when they are ill they become stressed, depressed and recover far slower.
I do totally agree that all female rabbits benefit from being neutered to prevent hormonal issues and also uterine infection and neoplasms.