Again, peg has nothing to do with pairs. Peg is the fact every BUSD can be redeemed for 1 USD. It doesn't matter if there are premiums in certain pairs, 1 BUSD can always be redeemed for 1 USD. The same applies to USDT, there were over $20B worth of withdrawals from USDT through their official site and every USDT was redeemed for 1 USD. That is the peg.
What you're talking about is lack of liquidity but that has nothing to do with pegging.
Anyways the move Binance is making will probably benefit all users as all pairs will be more liquid.