Very well could be the case. The B20 has those push rods and rockers tapping away constantly, like a nice mellow sewing machine noise to the human ear, but the the computer, trying to sift through all that noise to hear the detonation might not be easy.

On the B230, which is generally quieter to begin with, they had to start using rubber 'valve hushers' when they first put an ignition system on with a knock sensor to retard the timing for bad gas. A little rubber noise reducer that sits on top of the valve and pushes the lifter bucket up gently into the cam to reduce valve noise.

It might be possible to tune the valvetrain clatter out. What sort of knock sensor driver are you considering using? I know MS supposedly has an add-on KS unit now, but the one person I know of who tried it didn't have much luck with it (on a 16V turbo B230). Other than that there's the Knocksense, but on a B230 those just seem to go of whenever the revs get high regardless.

I can say, however, after damaging a few highly boosted B230's, you don't always hear what will break the engine. It's not always audible like pinging.
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)