It's just an opinion, I assume. Or you have any market research to back it up? I'd say "hype" has more to do with people buying biggest possible phone than anything else. But again, it's just an opinion.
The rationale for large phones is well documented in emerging markets where it is the customer's only computing device. Over the last few years, that has been a growth segment ("next billion") relative to the saturated US/EU smartphone markets. Apple followed Samsung's market leadership in phablets.
Other than Apple itself, market data on cross-device ownership would be hard to obtain, since the iPad is the dominant tablet. By definition, it would be a subset of the larger smartphone market. But the adoption behavior of this subset has strategic value to Apple, since it could extend Apple's iOS and phone silicon investments to compete with Intel in laptops.
A hypothetical (2018? 2019?) "always-connected iOS laptop" would again alter device portfolios.
