HGV signed route through Melbury Abbas A350 s/b

Can someone tell me what the whole idea of this route is where it takes you off the A350 if coming s/b at Shaftesbury and takes you through Melbury Abbas and through single lane sections which just fit a truck through and cars have to reverse back at pinch points?
I’m guessing it’s to stop trucks coming down the A350 and meeting trucks coming n/b at that pinch point where them houses stick out and you can only fit one truck through but surely the signed route s/b for HGV’s is worse? I think so.
Also how long has it been signed up that way as the last time I came from Chippenham to Poole there was no diversion route for trucks coming s/b.

Some genius or multiple geniuses from the council decided it was best to route lorries like this. Loads get stuck and there’s a local group who love to plaster that over social media.

Just ignore it and stay on the 350 its better than the diversion. Not sure how long its been signed, must be more than 7-8 years or more

Is it back open now? I used to do night run through there. I’d rather go that way than go A350 that route is tight as hell and can’t get over 15mph.

Today (9/2/24) coming down the A350 heading to Poole admittedly in a coach not HGV although i do deive HGV too. Noted Matrix sign stating HGV for Poole follow signs Melbury Abbas. Left at Roundabout then turn next right. Unbelievable whos idea is this and whoever came up with the idea have they ever driven a large vehicle because if they had they wouldn’t send anything large on that road. You approach a blind right hand bend i had to tuck in close to N/S edge so vans could squeeze passed me tucking their mirrors in. Once they had passed i then proceeded sounding my horn. Definitely not ideal. Not sure what the issue is on A350 to send you this way but surely cant be as bad.