I did hear something to that effect, but it's still illogical considering the demographic the books were geared to. Plus, it insinuates that there's something improper about a girl's completely natural and inevitable development. Why bother with brief allusions to breast growth if you're not going to bother going further? If Mary Ann needs to buy a bra and Stacey has "filled out the top of her bikini", as she brags in one book, then puberty has clearly begun and they are highly likely to reach menarche any day now. And they often discussed and gossiped about bras, so never mentioning menstruation--again, especially at that age--makes no sense.
And if she wanted it to be "wholesome", why bother tackling major issues like illness, death, and racism? These are okay, but a girl starting her period isn't?
Again, that's why I was impressed that the "Twins" series averted this.