Sorry, can’t find photos. Designed and built my own twenty plus years ago. Initially for TD bike but can do sport tour size. A zillion miles on the thing now. Entire bed drops dead flat on ground. Guide channel to front chock. Ride in. Get off. Two straps. I do not ride on slab at all. With this trailer can get to the good stuff wherever and be quick to ride always solo. Can operate in much less space without ramp. Definitely advantage IMO.
I can see it on a dedicated bike trailer with rails. That style of trailer can be scary because there's no deck to stand on while putting the bike on and tying it down. For a trailer with a deck I'd prefer a ramp.