If that helps to compartment knowledge in order to further UK security, one can expect it, eventually.
Nothing is scarier to me than a distant techno landscape where knowledge in irresponsible or irrational hands can be used for unimaginable horrors. Such extreme measures as censorship of undergrad STEM education would, in such a case, seem appealing to authorities.
Encryption offers table stakes for weaponization of math. I do, however, agree in spirit with your slippery slope arg