Tuya Local or NOT quite! (Standard Firmware NOT custom)

I’ve been playing around with trying to get my ESP chipset based Tuya devices setup LOCALLY with decent success. I’ve followed some good guides and read some good posts on this forum & others to get localtuya setup. I have 5 different smart plugs and a couple of bulbs working under local control which operate MUCH faster than via the apps.
I watched a Youtube video about this topick recently and the guy mentioned that even though his devices operated locally that if he disconnected his internet then after 5 minutes or so they became unresponsive!!
I decided to test this and found exactly the same issue which I could not get my head around. Anyway a few hours later it suddenly dawned on me what could be causing this. Even though I’d removed any way for the plugs & bulbs to communicate with the Tuya cloud server by unplugging my internet, my smart phone was still connected via 4G and all the devices had been initially setup using my phone. So, I switched of my phone then unplugged my routers internet connection again and waited, after 5 minutes my devices still worked BUT reaction time became VERY slow.
Can anyone explain my findings?
The way I see it, local control using the NON custom firmware method is not completely local or am I doing something wrong?

Doubt your phone is related.

My guess is if those devices can’t connect to their cloud servers they timeout or reboot after 5 minutes.

If you want pure local control (which I agree is a very good thing), flash custom firmware. Depending on device, you can maybe use Tuya-Convert to do this without any soldering.