It may not have been over HTTP, so possible to be sniffed. Or, even if it did have HTTPS, it might not generate keys in a secure way (or might use the same certificate as other devices). And you don't know if there are hidden backdoor accounts that might be found eventually...

So, yeah, it makes sense to block it - personally I block IOT devices from the Internet entirely (and don't let them initiate requests to my local network even) and use a VPN (IPSEC/IKEv2). That wouldn't work for devices that connect to cloud services, so I'd have to set up new firewall rules if I got one of them.