Our Discord community consists of peeps that are Furries, as well as peeps that are not Furries.
Most Furries do not mind NSFW Feral content (as seen with our partners), but peeps that are not Furries and want to make games with Anthro or Furry characters are not as inoculated into the fandom.
The rule is an extension of the rule in our Discord regarding NSFW Feral content to avoid friction with peeps that would otherwise have an issue with the content within our community.
tl;dr - it's a choice made to accommodate tourists interested in making Anthro/Furry content since not everyone that wants to make Anthro/Furry games are actually Furries themselves.
For the record, I am personally good friends with Feral Furries and MLP-peeps and don't mind their content and have apologized profusely with individuals like yourself that were interested in our server but realized the rules would disallow some or all of their content.
I apologize for the inconvenience.
There is a Furry Gamedev server (Furry Game Developers) that is perfectly fine with NSFW Feral content, and I hope we can partner with them on Discord soon so peeps have a place to go to share their content even if it is NSFW Feral.