The reason was probably that their 'Fenzys' had the corrugated inflator hose on the right side.
Until 1980 all single hose 2nds of Spiro came from the left.
From 1980-1982 some models had the hose connector on the right side, probably for American market where the 'Fenzys' had the inflator hose mostly on the left side.
From 1983 on all Spiro 2nds had the hose connectors on the right side, because, a.f.a.i.k, all 'Diving Jackets', which now came on the market, had their Inflator Hoses on the left side......