It is possible to replicate in vanilla. That video was made recording a vanilla gameplay. There are some other videos going around, like MacroBioBoi's. All of them made in vanilla D2.
Yeah I think that's mostly/only big news for speedrunners. Baal waves can be quite tough with untwinked and underpowered characters.
But any twinked and/or more optimized character around here will only run Baal for XP or in some farming event, and for both uses the waves are indeed much more beneficial than Baal himself.