That's false. Once again there is no "accept" or "continue" button. If you initiate a conversation and couldn't see the profile picture until they replied back it's because you weren't on their contact list and they added you to their contact list using the "add" button.

https://i.redd.it/8mvd3ez9gmm81.jpg

That's not the same as "accepting" a conversation request like for example it works on facebook.