This is originally Warren's advice and my humble experience.
Warren said some words about - keep master bus "clean" - so you can mix better and there is no interference between plugins - possible interferences.
At least you are fooling yourself with tons of plugins on 2bus 🙂
I had to make that experience too - attempt of quick "mastering" via 2bus gone wrong. Compressor plugin caused additional reverb - not nice !
Since that happened, i am always mixing with clean 2bus and do extra step with "cheap" mastering on printed mix.
That 5 minutes for create new project or change the DAW - It is worth it !