Intel ship DPTF drivers for Windows, so the appropriate thermal policy is configured at boot time. If you install thermald then Linux will do the same.
In the case of T480 the limit is specified by whether the laptop is in your lap or on the table. In the latter case it allows a much higher limit.
This check doesn’t work on Linux, so for safety reasons the former limit is enforced.
The computers don't break on Windows, why Linux uses should take this overly conservative approach that limits the performance of their computer?