The format the Samsung flips use I feel like solves your issue.

Nobody cares about how hard it is to hold, otherwise we'd have 4-5" screens rather than the phablets that are the norm and basically the only option.

Exactly. Remember when people, for years, complained that phones, for years, kept getting larger and larger?

It's the difference between stated and revealed preference. Phones kept getting larger and larger because larger phones sold better.

Though apparently we have hit the sweet spot a while ago, as phone size is stable now.

There is no point in history at which larger phones have sold better.

Sadly the iphone minis did not do well commercially, at least as we're told.

Must have been a conspiracy then.

Compare for any version. iPhone/Pro always sell better than iPhone Plus/Pro Max.

There is no year in which the larger size sold better than the mainstream size. Ever.

You are literally just making shit up.

You are comparing cheaper phones with substantially more expensive ones. For a meaningful comparison we have to compare phones with a similar price but different size.

False and irrelevant. The claim was "Phones kept getting larger and larger because larger phones sold better."

That claim is demonstrably false. Whether attendant facts like adjusting for price point lead to a subtler inference does not change the absolute fact that the proposition is not consistent with reality.

Price can decrease sales even if size increases sales and price and size are correlated. Causation doesn't always imply correlation.

Again, completely irrelevant.

The claim is "larger phones sold better."

That claim is flatly, objectively false.

I meant of course larger size causes more sales.