The only way I can find to solve this is to use display: inline-block;
for elements like this, but I'm not certain that's preferable (and it exists within some fairly common styling, so it could have impacts elsewhere).
The most significant thing IMO though is that this is iOS 9 we're talking about and it doesn't seem to be affecting anything else. We officially only support the two most recent versions of any given browser, so in the case of iOS that's effectively any iOS 10 and iOS 11 devices, and we're quickly approaching iOS 12 so it won't be long before we no longer consider iOS 10 to be supported either.
I know with iPads and such there is the point that there's a limit to how much you can update them but the iPad 2 is 7 years old now so I don't think it's unreasonable to consider it unsupported, and indeed that is what Apple themselves have signalled by no longer providing updates for that model.
So I think we'll just have to chalk this one up as a browser issue, unfortunately.