jm %µ Hk&T¬5Z÷ÍÃNæHÒúÒpp"}NL£Wallets have to estimate the chance of sudden congestion (on BTC). That chance leads to overpayment. This is what Core explicitly wanted as is working as intended.
https://whatsonchain.com/tx/6f28551fd19472c3f9a28e3af003422aa0b792df461c65e60f9f4bca1c4a06a1