This just sounds like a morning person trying to imply that night owls are unhealthy.
I consistently go to bed around 2 and wake up at ~10. I have better 'sleep hygiene' than many people I know who are 'morning people' because they force themselves to strict wake-up times.
Even with a good amount of sleep at consistent times each night, I am still more intellectually productive in the evening than in the first couple of hours after waking up.
I wondered if anyone would interpret it like that, but I decided you would give me more credit, given I was speaking from a professional POV.
Before I did the teaching courses, I would have described myself as a night owl. I did then (and still do now to a lesser extent) have poor sleep hygiene. However, since I became more wary of how illogical the dichotomy is, I have found I'm just as productive in the morning provided I've slept well.
In the morning, your brain is fresh from sleep and flushed of toxins. Your energy levels are higher and you've been hit with blue light indicating it's the start of the day. It makes sense that you would learn better in such a state.
What's the argument for night owls being better learners at night?
I would say that the argument is that many people report this to be the case and there are some studies pointing to the existence of such an effect (sometimes called chronotype). Even in the absence of rigorous studies, a reasonable default view is to say that such an effect may or may not exist and we just don't know for sure if it does.
I would argue that the burden of proof is on the person making the claim that this effect doesn't exist, as that's a stronger statement about the world. It also seems to contradict a lot of anecdotes without proper evidence that casts doubt on their accuracy; the simplified model that you mentioned, about sleep flushing toxins from your body may not capture all the relevant aspects here (for example genetic components to concentration ability).
Wikipedia references a few studies, but I'm not an expert and can't tell how conclusive or rigorous they are: https://en.wikipedia.org/wiki/Chronotype
That your 'brain toxins' and first blue light are irrelevant to many people's abilities to learn. Also, being a night owl doesn't mean you aren't getting blue light while you study.
I've been thinking about whether it has to do with the daylight/sunlight and my inability to "settle down" and concentrate when it's light outside. This "condition" is causing me to stay up late and lose hours of sleep per night. I've been thinking about going to see a psychologist or therapist to see wtf I can do to rectify the situation.