The point is though - you don’t get anything at all until you actually attend classes. So taking a gap year means having to fund it yourself, or have generous parents but what this comments author describes is closer to ‘normal’ - a large number, not necessarily a majority, of 18year olds will plan out a gap year contingent on taking a part time job at some point and then using that to fund travel or something - before taking up a place on a course (and hence receiving the money)
If you have luck/motivation/connections/skillset - you might find a job related to your (future) degree too. I knew several people on my CS course who worked IT support at a local office for a few months whilst living with their parents - then set off on a backpacking trip somewhere exotic.
Everybody can have a loan for the full cost if they want one, people from poorer families get outright grants instead.
Certainly not perfect, but my impression is it hasn't significantly hindered uptake from lower income students and its not a major financial burden in practice.
Obviously it's easier with rich parents, but it doesn't really require as much cash as you're imagining. It's pretty common to work a little first then use all the cash to travel later for example, or to work while you travel, e.g. by teaching English (TEFL - https://www.tefl.org/blog/why-tefl-on-your-gap-year/).