Sure you have to enable E2EE but they never say they use E2EE by default, they’re not advertising at all anyway. Saying it is “not secure at all” is a bit of a reach. They have proven they don’t share data with governments and again, you can use E2EE if you want
Easiest seems to me just enabling E2EE in telegram since it’s there. Asking to use secret chats seems easier than asking to switch plattforms