Hi Rosieragdoll
Yes I think that it's just to be more of a precaution really with worming of kittens even tho the cats are indoor.
Somebody mentioned on this post (sorry can't remeber who) that they need worming once a month til 6 months & have to say I agree. Once they have their worming tablet at 12 weeks I have always wormed once a month til 6 months then I do every 3.
Not sure if this is right but something to do with giving them better bone density & again prevention is better than cure.
Good luck with your 1st litter I know how daunting it can be but with places like this & other breeders to talk to it does make all the difference for sure.