I tow my Y boat backwards ,
for me makes launching & recovery much easier saves waves crashing into or over the transom & your pointing the right way before you start ,
another good point is it stops the engine from bouncing about at the end of the trailer if on dodgy roads,speed bumps ect ,
lucky for me i can use my trailer whichever way i want to or how it suits ,though if travelling a long way i use it with bow forwards & it only takes a min to turn the boat around anyhow as long as you deflate the keel .
Depending on what the local stations conditions are theres a few different types in use ,
some Most D class trailers for launching dont have a central spine but a U shaped trailer chassis to allow the engine to run without clobbering the prop & rollers fitted on the bunks or a V to allow Prop/leg clearance.
Down side is if towing backwards as in the case of most RNLI inflatable boats that have White retro reflective tape on the bow which can from the rear contravine traffic lighting regs ,but unless operational rnli boats should only travel on public roads with the full boat cover on.
(bottom pic Light bar & frame is removable )& for road use only.