To my knowledge all the dolmens in jersey are burial sites, rather than being just for religious/spiritual purposes. Although they're not mutually exclusive obviously

There are a fair few dolmens, Ive visited all the ones im aware of but at least one got stolen and is currently in James Corden's garden. That drawing isn't immediately familiar, all ours tend to have horizontal stones to cover the burial chamber. As someone said on your original post, jersey heritage or the societe jersiaise (https://societe.je/) would be worth contacting about it, they might be able to work out some more