Why is sodium the only allowed mod for 1.16.1? I have sodium+krypton+phoshpor+lithium and even then I'm getting constant fps drops because my computer is very bad. And why is only one specific version of sodium allowed?

Why is sodium the only allowed mod for 1.16.1? I have sodium+krypton+phoshpor+lithium and even then I'm getting constant fps drops because my computer is very bad. And why is only one specific version of sodium allowed?