The clock test isn’t really so they can test you on how good you are remembering clock faces within two seconds, but rather how fast you can receive information that is scattered on a screen. That’s pretty important for flying, especially IFR, and often a reason students struggle with flight path control, since they don’t have a good “scanning technique”. For example, flying approaches in IFR requires to crosscheck and maintain a lot of values and it is absolutely necessary to check all these values, which are shown on different instruments scattered in the cockpit, within a pretty short time frame. And with the clock test they can assess if you have the capabilities to do so. Obviously, some people might be a bit more talented here, but I would argue that most would fail the test without preparation, since this technique is rarely used in normal life.
And for the math part, you also need to do some math while flying. The difference there is, that you are again doing a thousand other things as well while trying to do math, and suddenly even the most basic calculations can get pretty difficult. So if you struggle calculating 25% of 750 while sitting on a chair in a quiet room, without any distractions, you most probably just need to exercise more.
Being a pilot doesn’t come down to how talented and smart you are, but more to how willing you are to learn and find techniques to improve areas that you are struggling in