The valves have to be the width of 1.5 envelopes apart so they can’t go any closer to each other than they are, otherwise they will heat each other by radiation. Then there is the small double triode at the front to think about. It can’t go any further forward or its socket would foul the lamp or any further towards the power valves due to heating by radiation. The valves are equally offset from each of their respective output transformers.
The problem you are seeing on the photograph, is a much bigger one: the controls are offset to the right from the three valves. IMO it was an unforgivable error on my part, and was so easily avoidable given a bit of forethought and some old fashioned ‘measure twice, cut once’ policy. I suspected that somebody would notice it eventually, but what’s done is done and I’m just going to have to suck it up I’m afraid, because there is no way I’ll be rebuilding for the sake of three slightly misplaced control mountings. Let’s just call it a lovable quirk.