There are a number of bugs/issues about brewing stands and mcmmo alchemy.

As per the default config of the mcmmo plugin, mcmmo alchemy experience is to be rewarded upon the completion of any proper brewing attempt; 15exp per awkward, 30exp secondaries, 60exp when modified by either redstone or glowstone, and 120exp for splash(gunpowder).
At MineRaze, however, this is not the case. Not only is mcmmo alchemy busted, but vanilla potion brewing is also broken, and brewing stands altogether might not be working as intended. In fact, most of the following issues have been previously reported by other players, but remain broken to this day.

June 2017, xdanox123 submitted a bug report and video demonstrating that brewing with gunpowder could be abused to gain massive amounts of alchemy experience.

June 2017, _Wenzer also submitted a similar bug report and video demonstrating that experience was not being earned when brewing.

July 2017, I posted a thread explaining that, contrary to vanilla and as a result of the LWC config, hoppers would not push water bottles into brewing stands. This can be corrected with a small line of code("brewing_stand: enabled: true" to protections.blocks in core.yml)

Splash potions.
In vanilla and at every server I have ever been with mcmmo plugin, 1 gunpowder can be used to brew any 3 potions into splash. At MineRaze, 2 gunpowder are required and consumed to brew any number of potions (1-3) into splash. If you use 1 gunpowder, the ingredient is consumed, alchemy experience is granted, but the potion(s) remains unchanged. You can repeat this exploit over and over, for example, brewing 1 gunpowder with 3 potions, and earn, for some unknown reason, 3064 exp! 3 potions brewed through all the stages at one stand should only yield a maximum alchemy experience of 675..
Needless to say, it is hardly refutable that the top in mcmmo alchemy have abused the gunpowder bug. For instance, a player (who is also a moderator to boot), had over 1000 alchemy only within days of the recent reset. Implausible.

Secondly, 1 gunpowder CAN be used to create 3 splash potions, only by initially brewing 1 gunpowder with 3 water bottles producing 3 "splash water bottles" that can then be brewed into "awkward splash water bottles"?! Busted.

TLDR: Alchemy exp is only being rewarded by brewing redstone, glowstone, or gunpowder.
Splash potions are altogether broken.
Brewing stands are hindered by LWC plugin.