It definitely loses its effectiveness against armor this way, but it's still a solid rod of metal, and quite painful to be hit with - so it's somewhat closer to a truncheon or baton, it's more something used in a police or bodyguard context for disabling and potentially capturing someone rather than necessarily for killing (although you could probably inflict some pretty nasty bone fractures like this).

https://www.mandarinmansion.com/item/antique-chinese-bronze-mace

Forked guards are also going to be helpful with binding against an opponent's weapon and controlling it, like in parrying daggers used alongside rapiers, although not all examples have them, some are basically just a metal rod with some added material to act as a grip

Them being called maces is just a historiographical quirk, they don't really have much to do with proper anti-armor maces. It's like this being called a "Khyber knife" - it is neither a knife nor actually related specifically to the Khyber Pass, rather being a more generally Afghan style of shortsword, but it's just a name that's stuck around in English-language historiography because some Brits back in the 19th century decided to call it that.

If it's anything like a sai, it's more of a club that just happens to have a thrusting point that will hurt like a motherfucker through chainmail.

The crescent version would be useful for hooking a shield, but it might double as a sword breaker too.