Well...had an interesting Friday looking at the car.

No idea what the heck the shop was looking at. There are two compressors available for my car, which they definitely were aware of:
64529185145 which has a magnetic clutch
64529185144 which does not have a magnetic clutch.

They informed me mine had the magnetic clutch, and it was in fact the clutch that was bad, as it wasn't engaging. They also quoted recharge with R1234yf after replacement.

Got eyes on the compressor Friday, and the sticker on it is 64529185144, so NO MAGNETIC CLUTCH, and also states R134a. So they couldn't even figure out the right freon or compressor, and completely mis-diagnosed the issue since the compressor is visibly spinning all the time, as there is no clutch, so no idea how they concluded the clutch wasn't engaging, as logically if one was under the impression that there was a clutch, it looks like it's engaged permanently.

Played around with ISTA again, and I am able to activate the "compressor control valve" and hear it click. Obviously trying to activate compressor clutch, which I had been trying to do previously, did nothing as there is no clutch. And since I spent all day on it, I'm now seeing JBE reporting refrigerant pressure of 0 bar, so my guess right now is it just needs a recharge.

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'08 X5 4.8i - 196k
'15 i3 REX - 95k - Blown AC compressor

'98 323is - 170k - Garaged
'94 325i - 208k - Sold