2 more laps after all this confusion...
K4 - 18"22 (session)
B4 - 19"44 (session)
Both laps had new records in early december, then I discovered that glitch in emulation on the Flash Cart and decided to not release them like that. Unfortunately that glitch was apparent in all of my records since the 2020 comeback, including K2. It didn't immediately catch my eye (wish it did) but once I knew it was there, it didn't sit right with me to have not properly emulated runs as WR's so I've decided to nullify them. I've also deleted those WR posts in here, kept all the dates though for future WR history purposes as the records themselves were all legit of course.
Anyway, I've decided to at least put work into these 2 laps again and was able to polish them up a bit more. K4 was ridiculously frustrating. This run shows the best viable console strat in a very satisfying run and yet it's still 0"30 behind the TAS! That is to be expected though with so many ice sections, some of them (especially the jump) are just uncontrollably hard. B4 was easier though I've realised an interesting thing here: The combined boost time of 16,8 seconds is not enough to cover the whole lap, so it's very important to space out your boosts. I guess that's nothing new but I've noticed a big variance in my laps and that had to do with just that: If you go really fast, you're getting closer to that unreachable point of not losing any boost speed. That of course is not possible, but it makes a small difference. It feels like you get an extra reward for going fast, by also staying a tad longer in that higher speed range. It's just a strange effect I've noticed that explains why you can easily fall back into 19"5x/6x laps while your driving wasn't that bad. On the other hand, if you get a really tight lap all around, you can observe the opposite effect (that laps are suddenly faster than expected). 19"39 is definitely doable here as the first few corners weren't that great.
Also: As a new form of proof it's good to also upload the time attack sessions, which I've done for these 2.