EDIT--warning! I don't have a clue, and am just asking, so don't ASSume nothing is wrong just because I am wondering about it!
Fuses are supposed to be sized for the wire's ampacity per AWG. If the wires to the fuses are proper for 15a DC fuses, then isn't that ok?
If somehow more amps are drawn than that, then a fuse should blow, perhaps they would both blow. As it is they are not blowing and everything works.
Is there really a safety issue here at all? It does look like "they" tapped in the awning with the lights (or vv) somehow looking for a pos and neg to connect to, and somehow got into two circuits for the pos side.
On parallel fuses, note that some inverters have twin wires for pos and neg (four wires total) If you use one fat AWG wire for the pos you can put say a 300a fuse on that OR use two thinner AWG wires and put a 150a fuse on each wire.
If one wire went, all the current would go on the other wire and blow the 150 amp fuse on it
