They've already done one though, if that isn't good enough then that test needs to be changed rather than add another, optional, test.
The first Test simply demonstrates that you've achieved the *bare minimum* standard to be allowed out on the roads in control of a vehicle, that's it.
And for car drivers, that *is* it, when you can show you can do that bare minimum, there's absolutely no requirement to even demonstrate it again unless you do something sufficiently stupid to get yourself banned and have to do a retest, so you can get into all sorts of bad habits (which you're probably not even aware of), let alone even read a copy of the Highway Code again.
Making the first Test harder isn't really going to make people remember anything more once they've done it, the only thing that will is making them have to demonstrate subsequently that they still know it.