Can't get your point clearly but binance is trading platform so they don't take price from other bitcoin exchange platforms.
They have USDT-BTC pair where buyer/seller set orders to buy/sell bitcoin and bitcoin price there is in terms of USDT not interms of USD like in Gdax or coinbase.
USDT always tend to maintain 1:1 exchange rate with USD but sometime it might valued lower or higher than that.
IOTA-BTC pair might have moved up so you can't get equal amount of IOTA from those bitcoin you have got after selling IOTA in past.
I wrote a big long explanation, and then finally so the BTC/USDT price on there! That explains a lot. Does the BTC/USDT not move as much as the BTC/USD price? I would have thought that if BTC/USD went up 10% then the BTC/USDT would too?
Thank you for your time.