Our council completely cut swimming lessons a few years ago, so unless parents can afford to pay, we've now got a lot of kids who can't swim. Even at 12 or 14.
And I would not ask any child to use a tampon who wasn't ready for them, I didn't start until I was 16 or 17 and found it painful even then at first. Have not been able to use any since the birth of DC2, but wouldn't now anyway as a friend of mine had TSS and almost died. When tampons work, great. They don't for me. And I know a lot of younger girls who don't want them either. I see nothing wrong with that.
As for the swimming lessons. Yes, the girls are disadvantaged here because of their biology. However, it is in the nature of this type of business that they need to fill a certain number of slots in order to make lessons financially viable. There are also no refunds for missed lessons for other, equally understandable reasons, because the money you've paid for the block is already accounted for and the lesson has happened ie costs have occurred to the swimming instructor and/or the pool. It is different if the lesson itself is cancelled of course.
This principle also applies to my children's judo and tennis lessons - booked in a block, paid for in advance and if you miss any, your instructor cannot sell the slot to someone else because these are regular slots (and your girls aren't missing the exact same time in the month, so not even a timeshare type arrangement where someone else books that one slot would be feasible).
I understand your frustration though, it always is such a waste when we miss any class we've paid for. I also understand that you're pondering how fair this is for girls in general and for your daughters in particular, but this is I'm afraid one of those situations where they do have to learn to navigate inhabiting a female body in a world where the default is male. That's not an accusation of a big bad patriarchal conspiracy against girls, it's simply an observation. A world where the default is female would of course have developed methods of accommodating young girls learning to manage menstruating and this issue would not have arisen at all.
Although I do agree with PP that we should empower our girls to make sure that their bodily functions don't hold them back, I also agree with you that this can be difficult at first. I was normally ill during the first few years of menstruating, so swimming was never an option for me and I sat the lessons out (school lessons at age 15, still had to attend though).
I hope you find a solution that works for you and your girls.