ChatGPT horribly slow in longer chat sessions.. but only in the browser versions?

ChatGPT’s longer chat sessions get horribly slow in the free version on my desktop browsers, both Chrome and Edge. As well as the browser on my phone. But TODAY I found out I can use the longest and oldest chat sessions just find on the ChatGPT mobile app (not any browser). Why is that the case? It hurts because I’ve been a long user and I know about this today.

Similar issue here: My longest running conversation gets so slow on browser version; however in the Android App it performs normally. I tried different browsers but it is basically unusable that way.