It's usually not very hard to remove the antenna on smartphones
Maybe so, but there is also WiFi, Bluetooth, RFID, NFC, and other connectivity modules to consider to. Disabling all of them without breaking the phone is difficult. It is far easier to start with an old laptop which does not have the majority of these at all and then just remove the WiFi card.
If you use the smartphone/ tablet as cold storage, I dont see an issue if it will by mistake connect to the internet at some point. Yes it is not the best that can happen, but it will not automatically download a bitcoin specific virus, that cracks your encrypted wallet in no time. Seems a little bit to paranoid to me.
Well then you no longer have a cold wallet. You now have a hot wallet which happens to be offline at the moment.
The whole point of staying 100% airgapped is to mitigate other risks that it is harder or impossible to protect against. Are you 100% sure there is no malware lurking on your device already? Are you 100% sure your device won't be targeted when you go online? Have you completely audited every piece of hardware and every single line of code in your device prior to using it? The answer to all of these is no. But if you can stay 100% airgapped at all times, then any such vulnerabilities will have a much harder time trying to steal your coins.