Beyond scanning a QR code phones are useless for most tasks regardless of how big their processors are.
This is silly. You can run whatever you want on a phone, and while more pixels and more real estate are better (he saw himself type on his 42.5" 4k TV) you can still do a lot with a small screen. Work is done with phones every day. It's of course absolutely true that most people are mostly consuming content with their phones rather than creating it, but that doesn't negate actual uses like CRM and data collection which are completely viable on a small-screen device.
Having all that processing power on the phone is mostly squandered, but it's handy for a lot of short-running, high-horsepower tasks. When was the last time you experienced a perceptible delay in loading an image that wasn't related to storage? And on the more expensive phones, even the storage is fairly snappy. I buy mostly cheap Motos and the storage is plodding on all of them, but I rarely do storage-limited tasks so it's only irritating when installing or updating apps.
The pocket computer was relegated to a simple calendar as well for the same reason.
Do you mean Palmtop PCs, or PDAs? Both have done a lot more jobs than that. I've known a lot of people who had sub-laptop PCs who did actual work with them. A friend of mine had a Dauphin 486 tablet-with-pen for example, and used it as his primary machine on the go. That had a kind of laughable form factor by today's standards, and it was amusing back then too to be honest since it was as thick as a GRiDPad 1910. Maybe thicker? Too lazy to look it up now, and I only have the gridpad so I can't just compare.
