That is not true. I have the official Tuya integration and local Tuya running perfectly in parallel for at least 1 month now. Both integrations control the same devices. Obviously they create different entities in HA, so it is a bit pointless to do so, but it is perfectly possible. I also have all my Tuya local devices in the smartlife app. They all work in parallel, each can controlt he same device, they do not interfere at all.
I was using the official Tuya integration, but got annoyed with all the delayed status updates, so I installed the Tuya local to try it out. I added all my tuya devices in Tuya local without removing them from the official Tuya integration or without disabling the official Tuya integration. In Tuya local I created new entities with the same name, but just added the _local suffix. This just works, no issue whatsoever.
I liked Tuya local so much I ended up updating all my automations and lovelace cards, but I still keep the official Tuya around mostly for scenes (which I use for my IR remote) as well as a backup in case something would ever go wrong with Tuya local.
I can control any device now with either the official Tuya integration or Tuya local. Like I said, there is no point in doing that, but you can safely try out Tuya local without having to remove the official Tuya or remove your devices from the Tuya app.
Here you can see just a snapshot of my devices. I have just 1 bathroom light, 1 entitiy is from the official Tuya, the other is from the Tuya local integration. They both work and both control the same light. And all these devices are still also in the smartlife app.