Fair enough, I do NOT mean to scare away anyone posting cool new things and options, so thank you for doing so. My response was only so that new buyers of the HAS and OSSC don't spend extra money when they don't need to do so.Update on above. Spoke to TianFeng about his HD15-2-Scart. Of course not much difference using his adapter other than more cost effective shielded cables over MiniDin to SCART for most use cases. However my focus was mainly with RetroTINK5X, which he confirmed can be a solid use case for TAITO F3, based on it's current behavior with OSSC, despite RetroTINK5X clearly being a different device that doesn't play well with SCART TTL. Now he can't guarantee this working since that's all up to the RetroTINK5X. For my part in all this, it's mainly for the name of science. I want to test it out. Looking forward to his adapter to arrive. Nice to have another extra tool for my tech kit.
If you have a HAS, the D15 adapter (you're correct it doesn't convert a signal, just adapts the connector), which by the way is an extra cost and you have to order it separately, you can play TAITO F3 games fine on an OSSC. The only thing you'll miss out on is the OSSCs low pass filter, as AV3 on the OSSC does not have it. But it's not really needed for F3 as the HAS has you covered.
IMO, you're just getting something extra that doesn't do much for you, but the adapter itself is very cool, useful in many other cases, and also helps with the OSSC not having a LPF on the AV3 input, as Bob mentions in the video. It's a cool thing, you just don't need it for the HAS!