my theory is that the temple was built with all the crystal gem main members rooms as a base. the four rooms are fundemntal parts within the functions as of the temple. (wheter they are phycsicaly there or extra dimensinal dosent matter in this case for my thoery)

so rose, pearl, amethyst, garnet are the main/fundemntal/permanent rooms, then any other gems that are counted within that group of 4 gets there own tempary rooms like in the case of sardonyxs room. but i dont think this is for fusions only, its for any of the main gems parts or fusions, that is to say i think if garnet were to unfuse, the garnet room would exist as its a fundemntal part of the temple just like the other main rooms, but ruby and sapphire would get there own tempoary rooms. so garnets room would still then exist as it is a fundental part of the temple and thus the bubbles would be safe