Very interesting, thanks!As it happens I have the answer my dear fellow; they are indeed made by William Lockie and the difference in fineness is present because it is supposed to be as such.
Let me elaborate a bit. After the discussion with our fellow @BMC, I followed the link that he posted which is found here below and I carefully read what it is written.
Differences and similarities between Lambswool and Super Geelong. Why we now call Lambswool "Geelong Lambswool". Why Geelong is always "Super Geelong".www.ahume.co.uk
After that, I emailed A-Hume to seek more information on the matter and clarifications because the key phrase and I quote is: “William Lockie now call their classic lambswool sweaters “Geelong Lambswool”, and they confirmed that this is exactly the case.
In other words, in whichever WL garment the label states Geelong Lambswool (as your Harvest Gold waistcoat and our fellow's crewnecks), the garments are in reality exactly like the old 100% New Lambswool ones, only now re-labeled. They come from the Geelong breed all right, but they are not Super Geelong (first clip, 19.5μ, finer gauge), hence the difference that you've just experienced. Therefore, my past phrase addressed to @BMC that there is no difference between Geelong and Super Geelong, they're exactly the same, does not hold true.