It's a (very) niche kink in m/m erotica, though the type is almost always the "original" version from SPN fic, with little variance from that mold. As in, extreme seme/uke (pack) dynamics werewolves plus mpreg, and focusing on the smut over any other potentially interesting elements.
I've personally found that fanfic has a lot more variety in the specifics of the alpha and omega dynamics, and what place betas have in it; it depends on how much or how little the author bothers to worldbuild, and what specific kinks and tropes they use.
In nearly all the published versions I've found, the takes on it are very generic and seem almost afraid to be creative with the concept, unfortunately.
I've personally found that fanfic has a lot more variety in the specifics of the alpha and omega dynamics, and what place betas have in it; it depends on how much or how little the author bothers to worldbuild, and what specific kinks and tropes they use.
In nearly all the published versions I've found, the takes on it are very generic and seem almost afraid to be creative with the concept, unfortunately.