In the end, same result. I guess it would be much harder to get a pack of stuff from Walmart onto a mission than something from a certified supplier who has a datasheet and certifications for the item. And having to order 100pcs of a very cheap product even though less would have sufficed isn't a good reason to instead have to certify tampons of unknown origin manually.

Just launching the space shuttle costed $24mio per flight (in 1977 money), so saving a dollar or two by buying fewer tampons was clearly not a priority.