In theory yes, but in practice probably not.
The 18 year olds (post A-levels/Gap year) aren't really competing against the older ones who are already employed at the firm and get an apprenticeship there (non-graduate one).
I don't know the numbers, and can only speak about the Solicitor Apprenticeship, but I'd be surprised if many 22+ year olds are going for Solicitor Apprenticeships. They are very much targeted at 18/19 year olds as a first job.
From the firms point of view why would you entertain a 22 year, who can't have a degree at that point, as those are that App reqs.
So, for the older ones who are already at the firm, then that may stop in the new world, so they'd need to get a degree via a different route. So, again, be surprised if the firms say "We were giving 1 App externally and 4 internally, so we'll now give 2/3/4/5 externally", because they will be extending their head count. The beauty before was that they were getting the quals/training for existing employees.
For the graduate version of the App, then 18 year olds aren't competing. Firms aren't going to suddenly switch to take on the equiv number of 18 year olds, as they would have had for the graduate version. They'll still take graduates via different routes.
It will still take some years for firms to decide if the trailblazer (post A-levels) version is better than the graduate routes.