I don’t know why you’re being downvoted for this. Even with CGNAT and related technologies, each modem still has a unique MAC address at the cable/DOCSIS level (even without loading Ethernet on top).

Where you could be wrong is buildings with large networks, say an apartment building with wired Ethernet to all the units but all being routed through the same WAN(s), but even still I’d hope that the network is managed in a way that it’s not hard to tell which unit is which IP internally. Unrelated but I’d also pray that each unit is on its own VLAN for security.