With the difference that in that case you switch out your special attacker and send in the physical to scare blissey.
In the Gothitelle scenario, you lose your tank for free and she can just switch out when you send your physical attacker. That's a pokemon killed for free for the opponent. Also, if you run another or more tanks, you are never going to be able to play them because of Gothitelle coming in. Shadow Tag is a broken ability and it needs to go. Countering a problem (stall being too strong) with another problem (shadow tag being broken and unhealthy) isn't the solution.
Gothitelle greatly threatens balanced team too, not stall only.