Blockchain – How are Bitkey’s spending limits enforced?

Block’s new Bitkey is a 2-of-3 multi-signature wallet (https://bitkey.world/en-US)

I’ve read the white paper which summarizes their intentions well, but doesn’t really go into technical details.

Basically, you need 2 out of 3 keys to authorize a Bitcoin transaction: phone app “mobile key”, hard wallet “hardware key”, and web service “server key”. From what I understand, n-of-m multi-signature transactions are natively (and natively) supported on the BTC blockchain.

However, Bitkey also says that without a hard wallet, it cannot authorize transactions that exceed personally set spending limits. (i.e., even if “Mobile Key” + “Server Key” is 2/3, your transaction will still not be approved if it exceeds your set spending limit.)

Is this feature natively supported in blockchain? If not (it’s just a set of policies for blocks/bitkeys) then in what ways could a malicious actor fail or exploit this? Could someone hack/tamper with Block/Bitkey’s servers so that I can send BTC over the transaction limit without a hard key?

(PS Sorry for this being a beginner question. I’m a developer, but I’ve never worked with blockchain before. I’m learning. If there are any further technical tutorials/guides on how to implement a multi-signature wallet with transaction limits in Python, I’d enjoy learning. Same goes for that).

thank you