I'm no lawyer, but I was under the impression that there's a certain point where even if you avoid using the exact wording, you can
still have enough similarities to where it becomes a potential infringement. For instance, take a look at the two versions of
chill touch. Leaving aside the identical names, both are a 1st-level spell, both are tagged as being necromancy, both have somatic and verbal casting components, both are touch-range, both call for a "Fortitude" saving throw, both deal "negative" (or "negative energy" for the 3.5 version) damage to living creatures, both cause undead creatures to flee, etc.
But that's really a microcosm of the issue, which is that Paizo's looking to get away from publishing under an area of uncertainty, and I'm not sure that there is one. My understanding is that there is no ironclad pre-trial litmus test that you can put a work through to determine whether or not it's infringing on something else; a judge or jury is the ultimate arbiter.
To that end, Paizo's choices are essentially to try and de-OGL-ify their works (which potentially includes everything they want to reprint) and
hope that WotC thinks that there's no infringement, or that it's at least not worth going to court over, or to stick with the OGL v1.0a anyway since WotC doesn't seem likely to try to yank it again (and that there's a strong chance WotC would lose on the merits if they tried and it went to court).
Either way offers some uncertainty. My concern is that de-OGL-ifying their work would be a huge process, one that's long and costly and ultimately doesn't end with them being any more certain of avoiding a court battle than they would if they'd just stuck with the OGL to begin with.