It is weird if this is the intention.
It doesn’t turn the chat to that GPT. It only works for that line you type. You have to continue to use @ and the GPT if you want that same one. Keeping an ongoing conversation will be difficult as you have to keep remembering to use the @.
Second, it works perfectly fine on the mobile app. As it should. It lists a fiew, and then a clickable text that says “…and X more”.
I use custom GPTs so much, that I can’t work like this. I am stopping my subscription to ChatGPT if this isn’t fixed soon as it a deciding factor for me.