As a scout main who plays scout in Highlander and 6s I can confirm that the brass beast is surprisingly good in both game modes. It’s a lot less common than tomislav or stock, but it’s still the third option and is considered to be a good strategy in last holds in 6s. And in Highlander brass beast flanks have actually happened where a heavy will kill half the enemy team and somehow not die.
I swear the chances of coming across a heavy main that is toxic and not chill is like winning the lottery twice before getting struck with lightning in the spine and a pig falling from the sky crushing your skulls.