I use their heavy horse rugs which have bags of shoulder room... but I don't know how their standard rugs fit. Adjustable front though and the one in the picture is on the tightest setting by the looks of it.
Yes it could just be the pic. Normal rugs don’t seem to rub him but he’s older and more muscle waste these days so I’m thinking the high neck might be more comfortable (which is a shame cause there are some lovely cheap fancy pattern ones)