I know it's the hardware because again, with "good calibration" your aim is good when standing perfectly still and essentially just on the actual calibration screen, if that, even if you're sitting and just slightly or not so slightly change your aiming pose as you play rather than actually move about. Hell, you can be calibrating while looking down the sights but then playing more sort of hip-firing rather than taking every shot so carefully, again the aim will be slightly off. From that point it goes off quickly unlike a lightgun. And it's impossible to stay perfectly still, you obviously move the gun around even just to aim at different corners of the same screen, so it's always gonna be a given degree off, a given degree of a vague interpretation of what you're actually aiming at. It also goes off if you change your distance as then you do different degrees of movement to aim at the same corners of the screen. Sure, you can technically adopt in some games, you can enable crosshair or use the bullet hit effect to correct your next shot after missing and end up using bullet hits like crosshair with lag, that's still not proper aiming like you can do with a real lightgun and hopefully the Sinden/Polymega lightgun too (and modern VR controllers). Games like Point Blank with some of their toughest challenges would be impossible to do with such a set up without crosshair on (like the falling leaf one with a single bullet) unless you got super lucky, unlike with a real lightgun where it's all up to your skill if you achieve it or not. Its up to you if you find that good enough or not but I didn't say anything untrue and you concede to it by calling it an "approximation" at the end so I dunno why I got that reply at all. It's impossible to have 1:1 aiming with just two points of reference for the Wiimote camera to track. Hence SEGA's later lightgun arcade games with LCD screens using waaaay more than two reference points to essentially do what Sinden does, create a whole border for the gun camera to track. It's not better in other emulators than Dolphin or native Wii either.
AimTrak is basically the exact same tech as Wiimote/GunCon3 so of course it's not worth the money in my opinion and yes it goes off just the same. Though Wiimotes are pretty expensive too these days (I don't trust third party stuff) actually, I was looking to replace mine a while ago looking for official stuff, it's crazy, even though there were plenty available still at the time since they had WiiU versions and everything (and if I was gonna get them I'd use them with more than lightgun games so wanted the Plus obviously). Each cost around 50 or more at the time.
Badly calibrated doesn't count as a comparison, this tech goes off even if you do it the best it can be done. With proper calibration you can theoretically do those Point Blank challenges if only you're good enough. With Wiimote/AimTrak/all I also mentioned before, it's LUCK if you ever get it right.