It's a new lease though, so the terms are free to change.
Deposit amount needing "topping up" cynically assumes the rental is increasing by more than the compounded interest on the deposit... which shouldn't be standard and tenants should use this as an opportunity to query interest rates.
Tenants should expect reasonable interest on their funds held in deposit by landlords or agents. The former tend to spend the deposit and sometimes don't have the cash flow to repay the principal, nevermind interest. Agents are better but they get away with a minimal interest rate, and of course keep part of the underlying earnings for themselves ("commission").