In the .json files for altar recipes, the serializer is astralsorcery:altar. however, its actual recipetype is astralsorcery:simple_altar, causing incompatibilities with other mods, such as crafttweaker.

The recipetype will be renamed to "astralsorcery:altar" in 1.13.10 onwards

There isn't actually a requirement to have them match. (Still a good change though.)

It was actually a limitation in crafttweaker that required the recipe type and recipe serializer to be the same. Could add the recipe just fine with datapacks or KubeJS.

Example being vanilla's crafting type is minecraft:crafting and two of the serializers are minecraft:crafting_shaped and
minecraft:crafting_shapeless but it has more serializers (one recipe type can have many serializers).

More information here: #1715
PR that relaxes the restriction here: CraftTweaker/CraftTweaker#1166