> Now they consider the waterproofing good enough to guarantee it.
Well, no, since liquid damage isn't covered by the warranty, there is no actual guarantee. There is a claim (and maybe a third-party certification) of meeting a particular standard, but that's different from a guarantee -- its marketing with no risk of having to pay out money if the performance isn't up to snuff in practice.
A guarantee puts warranty money where your marketing mouth is.
IP67 is not good enough for swimming (1m submersion). Note the emphasis of the watch being able to be swum with, but for the phone they only showed it being used when it was raining
Unless getting dunked in water, I haven't heard of anyone having any issues with water damaging their IPhone.