No, I'm pretty sure that's exactly the matter. Only Apple apps can multitask.
But that's iPhone apps, they were never intended or claimed to be truly open. Adobe is claiming they "openly published the specification" to PostScript, but they didn't. Compare that to a truly open standard like HTML5. Does Apple have a secret, proprietary API for that?
Of course they published the specification in 80's, it would be difficult to do anything without it, as PostScript is programming language (for a specific niche, but Turing complete).
What they didn't publish at the time was Type1, as they wanted to be the gatekeeper for publishing T1 fonts (see similarity to Apple?). It didn't take long and T1 was reverse engineered, despite the obfuscation.
But that's iPhone apps, they were never intended or claimed to be truly open. Adobe is claiming they "openly published the specification" to PostScript, but they didn't. Compare that to a truly open standard like HTML5. Does Apple have a secret, proprietary API for that?