The problem with liquid metal is that it is corrosive to aluminium (the heat spreader/"lid" of the CPU is made of it).
As a result, after a few months the print on your CPU may be illegible, which is typically equivalent to invalidating the warranty because the product can no longer be identified.
In addition, liquid metal has little advantage over normal thermal paste, unless you plan to "head" the CPU, in which case the warranty will be void anyway.
Hi
I checked again and it seems that Ryzen also uses nickel-plated copper and not aluminium as previously assumed (I had misunderstood the source referring to the cooler).
In that case, corrosion should not be a problem as long as you only use components with nickel-plated copper.
This is especially important in the case of the radiator, as it often has bare (non-nickel-plated) copper surfaces, and the cheap stock radiators sometimes even have aluminium, both of which can cause problems.
Another point of caution with liquid metal is the electrical conductivity, which is why I still advise using regular thermal paste.