I installed the Schlage Encode Plus at my mother-in-law's house when we were visiting over the holidays. From what I remember it wouldn't lock or unlock using Siri on the HomePod mini alone. I could be wrong about that, and maybe it will lock but not unlock? I don't have any smart locks installed at my house yet, so I can't verify. I do have the Meross MSG100HK garage door controller. I know for a fact it will not open or close the garage door from the HomePod alone. If you try it will tell you that you need to use a iPhone or iPad to authenticate or something like that.
Rather than do that I tend to just use Siri directly on my Apple Watch/iPhone/iPad. Usually my watch is easiest since it is already on my wrist and unlocked, I just push & hold the crown for a second to initiate Siri and tell her to open the garage door (I don't have "Hey Siri" enabled on my watch). If you are actively using your iPhone or iPad then you should be able to just tell Siri on them to lock/unlock the door. Otherwise if you are not using them and you tell Siri to unlock the door it will have you authenticate with FaceID/Touch ID before it will do so.
As others have said I am sure Apple did this on purpose so you don't have someone outside yelling for Siri to unlock the doors and getting in. I'm guessing they aren't confident enough in voice recognition to rely on it for authentication, or maybe they are afraid of thieves getting recordings of people's voices.
So my guess is if you can just tell Siri on your HomePod to open/close the blinds and it does it without authenticating thru your watch/iPad/iPhone, then anyone will be able to open/close them. I suppose you could try turning off all your watches/iPads/iPhones and trying it yourself.