The attributes ARE remembered for the product already in the cart.

It does not make sense to "toggle" this behaviour.

Here's why.

I buy a pair of SHOES that are available in BROWN and BLACK and sizes 7 , 8 , 9 .

So... my first choice is BROWN size 7.

But I really like that style of shoe, so I also want a BLACK pair. I go back to the product info screen, and then choose a size 7 in BLACK.

If the "toggle" effect was there, I would be FORCED to buy another pair in BROWN.