It does have that ability on the HomePod minis that I have around the house. If a timer is set on one of them and then I want to reset it or add minutes to it, I can do so (but only when that HomePod mini hears me).
The inability to set multiple simultaneous timers is annoying. I compensate by setting multiple alarms. "Delete all my alarms" works when I'm done, but it's certainly a hack.
siri definitely has multiple timers. BUT you can only have two though and it only works on Apple Watch and HomePods.
I know, right?
Also a little known hack to set a timer you don’t have to say the whole thing just press the Siri button or say hey siri ‘n minutes’ and it will set a timer for n minutes.
On Alexa I run many times simultaneously. Didn't know it was a special feature. I just name them.
Latest update(?) it quit announcing expiration by name if only one was running. Just beeps, and maybe I forgot what it was supposed to be timing. Annoying.
Especially annoying if more than one person in the house is setting timers.