I hope someone currently involved in admissions can confirm, but my impression is that applying after A levels is not a disadvantage, maybe even an advantage. If he applies in autumn 2023 or early 2024 for entry in September 2024, many universities/courses would give him a decision very quickly, as he would be a known quantity, with actual grades on his application, not forecasts, which may or may not be good forecasts.
If he doesn't apply to UCAS during his A level year, there is the option to apply during the period called Clearing or Adjustment immediately after the A level results come out in mid-August 2023. I would say this is only something to do if he's put in a bit of work in the weeks/months beforehand thinking where he'd like to go and which courses, as then he can spring into action on the morning the results come out with a clear plan and just a few targeted applications. People who apply on impulse and accept the first thing offered very often drop out early on as it turns out not to be what they really want.
Clearing is a way for universities to fill up the last places on their courses. Some courses that still have places available at that point may be less popular for a good reason, but that's not the only reason they may still be recruiting. Sometimes they have a lot of applicants who've accepted an offer but don't meet the grades. Those who are close may well get accepted anyway, but to those who've fallen well short the university will have to say no, and look for last-minute replacements.
Adjustment is a process for applicants who've done a lot better than expected to make a last-minute application to a course they previously thought was out of their reach. Not many people will qualify for this, or be interested, but it's worth knowing about for a really bright student who takes time to hit their stride. I did a couple of stints on the Clearing and Adjustment hotline at the university where I worked, and it was always lovely to get a call from an Adjustment applicant. Typically they would be saying 'I got A A A and I'd like to apply for Law' and there would be a good chance they'd get in with those grades. My university always offered extra places for Adjustment candidates on courses that typically didn't go into Clearing.
However, he doesn't have to go university. There are some excellent apprenticeships available and they have the huge advantage of coming with a salary and no debt.
Good luck!