Samourai announced this as part of their 0.98.87 update. Samourai attribute the change to increased time spent in customer support explaining ever changing fiat values held in wallets( as price of bitcoin/usd changes).
Samourai wallet will now show balances in units of sat (1 sat=0.00000001 BTC ). Their watch-only wallet will still show balances with Fiat conversion.
Source : Samourai Blog