My Fitbit has a "find my phone" feature that uses Bluetooth to tell the Fitbit app on the phone to make a loud whistle. It's kind of handy and ive made use of it several times around my house, but obviously isn't useful outside Bluetooth range.
MAC address, but devices don't care, by design they will connect if the SSID and encryption type are the same, actually, you can create a mesh wifi network at your house with regular routers or access points by doing so, connecting them with wired ethernet.
But it would probably be an annoyance in large multi hotspot environments, and could become another thing to train people to mindlessly click through like cookie prompts.
Fortunately many default network names at least contain some randomness these days, e.g. three bytes of an access point's BSSID, to make this less likely.
That's also the proper fix – pinning a WPA password to an individual BSSID would go against the concept of encryption being scoped to an ESS/ESSID, not individual APs.
Networks that are meshed by design take this into account and communicate about signal strength per client, handing them over when they notice a neighbor would be able to serve the client better.
(That's how it should work, not how it does in practice)
Presumably you could get a lot of random devices to automatically connect and then hijack DNS to cause trouble.
Initially loading and then synchronizing certificates across APs would be anything but trivial.
I've surprised my friends a few times by keeping my SSID + password constant over the years and across several moves within the city (and across ISPs) and even internationally – whenever they come to my place, they have Wi-Fi the second they step through the door :)
It's also nice not having to re-configure various embedded devices, many without a sane user interface to type a passphrase or even accept a new TOFU public key, every time I set up a new router at my family's place.
I don't know why more devices don't support WPA Enterprise, it's not _that_ complicated a protocol. I can imagine a "secure router" product with a normal WPA3 network for management and an "enterprise" network with a simple username/password list selling quite well in some niche circles.
You can build such a network yourself, though, with almost any OpenWRT device, though it's clearly not something most end users can manage themselves: https://github.com/ouaibe/howto/blob/master/OpenWRT/802.1xOn...
A Wi-Fi network is the abstract concept of "all access points using the same name and passphrase", not an individual instance of an access point.
If you connect the two access points (e.g. using wired Ethernet), clients can actually roam between the two fairly seamlessly without any other setup required, and this even works across brands!
You can only do that for unencrypted networks or those for which you know the passphrase, though.