Can aluminium be heat treated twice?

Are Ali frames heat treated after building? I didn’t know that - guess I assumed it was the same as steel in that regard, individual tubes are heat treated in different ways by the tube manufacturer, but the built frame itself is not then heat treated.

I still don’t really get the difference between adding a disk mount to a tube just after frames been built and now (except of course all the extra stripping and painting work). The same rules apply and the same standards are needed in the workmanship.