The LGPL requires that the end-user be able to replace the library with an API-compatible library and still run the program. That's arguably impossible with an iOS device, and certainly impossible if you don't provide at least object files that can be relinked. Even with object files (or source) they'd have to pay to register as an iOS developer.
I suspect the majority of developers using the LGPL don't realise, or perhaps even agree, with this intent, so you're probably unlikely to be sued, but it's what the license demands.
If the author wants to use a GPL license, its his decision. But using a viral license in a support library is harmful in any case, as it destroys all ability to use it in a program that incorporates other pieces of code that might not be compatible with the GPL.
This isn't news; this requirement exists on all platforms, not just iOS.