This has always been the bonus policy at VIPSports, long before they added the
RTG download casino.
Many (possibly most) sportsbooks have clauses like this regarding reload bonuses for sports betting. If your (withdrawals + current balance) - deposits is a positive number, you aren't entitled to reloads. The problem is that VIPSports is using bonus conditions that are well understood in the sportsbook community and applying them to the casino community, where a clause like this is very uncommon.
VIPSports states this condition very clearly in the bonus terms and conditions on their websites (VIPSports, VIPCasinos, VIPHorses) I do think that they should explicitly repeat this clause in a disclaimer at the bottom of any promotional emails that they send out. They currently only include a link to a bonus terms page. But overall, I don't see the big issue here.