IMO the supply for the black tank rinser should be totally separate and with it's own dedicated hose to prevent/minimize the possibility of ever contaminating an RV's potable water system or the CG system. (There must be a reason why RVs aren't built with the black tank supply interconnected with the potable water system.) Vacuum breakers in RVs sometimes do fail. If you don't want to change the setup, at least install a good check valve between tank inlet fitting and valve.
Some jurisdictions require a backflow preventer/anti-siphon device at a site's faucet to prevent contamination of the CG's water system like in
Minnesota for ex. In the OP's setup if the vacuum breaker failed or leaked and the CG did not have backflow protection at faucets, contaminated water could potentially flow back (under some circumstances) into the CG's system and when you turn a faucet back on inside the RV, contaminated water could get into your potable water system.
Don't know what the specs are for that blue inline filter, but they can be restrictive and the built-in tank rinser may not getting enough flow & pressure to work effectively. The fittings all look like garden hose type - valves and fittings in general can cause pressure drop and further reduce effectiveness of the flusher. I would have used standard 1/2" ball valves and 1/2" PEX or brass fittings and hose adapters. If using a basic exterior inline regulator, I would upgrade to something like the Watts 263A to get better control on the pressure. CG water pressure can sometimes be quite low and you need every single psi you can get and it's good to optimize what you've done for flow & psi otherwise the rinser may not do much. FWIW, you shouldn't need teflon tape on hose fittings, that's what the washers are for.
