I would argue that it’s not a binary option. Whether phone can or can not perform tasks that laptop can. It’s a set / range of different use-cases.
And as you said, even the glassy rectangle form factor took many use-cases from laptop. If the question is “can phone do all the tasks that laptop can do”, the answer will always be “no”. But if you analyse the use-cases and sort them by percentage, then I would argue that things like “browsing the web”, “editing documents”, “chatting with people” etc. will be the most predominant. And those are the tasks that current phones either can do or at least could do, if the appropriate software was developed for it. Yes, playing modern video games, photo editing, video editing, rendering graphics, programming and other advanced tasks would not be done easily on phone’s limited hardware, and that is why PCs, either laptops or desktops, will remain the device of choice for productivity. But as my initial point stands, the percentage of those use-cases is far outweighed by casual use-cases.