On mobile, totals on the Home tab (Net Income, Est. Net Worth, etc.) display the currency symbol, based on the original primary currency set for the account.

If the primary currency is changed on the web app, once you close and reopen the app, the values will be converted to the new primary currency, but the currency symbols remain the same as the original primary currency. If you switch budget account and then switch back, the currency symbol then reflects correctly. So closing and reopening the app doesn't fix it, but switching budget accounts does.