That argument is orthogonal to whether OLED panels boost sales. If OLED doesn’t boost existing sales for the iPad Pro, then it’s unclear why it should boost existing sales for the MacBook Air. It’s not like an “ungimped” OS somehow profits more from OLED.The real reason iPad Pro sales were not what Apple had anticipated is because they're still running a gimped OS, thus limiting the full potential the hardware is capable of. Why spend $1,000 on an iPad Pro when you can buy a MacBook Air for around the same price (or $100 less when the M3 13-inch MBA 16/256 goes on sale every other week)?
Of course, Apple could be wrong and OLED actually did boost sales for the iPad Pro, but other factors reduced sales. But then you have to explain why those factors didn’t already apply on the previous iPad Pros.