Nope, Siri can also do multiple timers. It asks for an name if an unnamed timer of the same length already exists.
A HomePod can set multiple timers. A Watch, iPhone, or iPad can only set one timer. There is no obvious technical reason for it. It just seems like only the HomePod team thought it was an important feature.
This becomes annoying if you have multiple devices set to respond to “hey Siri” and the wrong one picks up the request and then refuses to comply.
If I say "set a timer for 20 minutes called A" it just ignores the "called A" part.