Yes that is how it works. But not all features are available through Homekit, most notably you can’t set te state for Home/Away. That can only be set through the cloud API.

Be aware Tado just announced limiting access to the Api to 100 calls a day. Which is quite low. For full access you need a subscription for 5 euros a month. Perhaps read up on that before investing.

You can configure storage paths. That way, you can direct tags to be stored in a specific folder.

You can then get the files for the accountant from your file system.