All lenses even the Quicksnap have at least two air-to-glass interfaces.
Ian, it’s ok to say Single-layer coatings understanding that specifically means a 1/4 wave thick layer of Magnesium Flouride. So it means a specific thing. There are many different Multi-layer coatings, starting with the primitive designs of the 1960s, but they are all related in the fact that there’s only a handful of materials used in designing the layers. See the sticky post I made on the details of coatings somewhere here in Photrio.
I thought multiple coatings, wellinitially two goes back to just before WWII and a Zeiss Patent. I think the problem is many use the term Single coated for all pre- Super Multi Coated lenses, and other manufacturers equivalents. There's a blurring of terms because there's been a fall back to using the term Multi Coated to encompass the more modern extremely well balanced coatings.
So there's not a simple term that encompasses the lenses with early balanced multiple coatings to help with colour balance, I think introduced late 1950's rater then early 1960's but with CZJ it's the 50mm Pancolar arenamed Flexon with thenewer coatings and the Color Skopars from Voigtlander.
No-one really compares coatings, I've owned I think 7 203mm f7.7 Ektar lenses 6 British made and the changes o=in cotaings is quite marked. The oldest are/were in Kodak Epsilon (Ross) shutters these are in Kodak terms Lumenised, then newer ones in Prontor SVS shutters have improved coatinds and that's improved as well. I don't have a very late version in a Compur #0 they are quite rare, although I do have a very late US made version in a Graphex Compur #1,with excellent coatings. So one lens and a progression of improvements in coatings, and being a Dialyte coatings make a huge difference. The pre 203mm Ektar the uncoated Kodak 203mm f7.7 Anastigmat was never sold here in the UK, Kodak Ltd only sold British made lenses after WWI until they bought Nagel who used initially Schneider lenses becasuse Nagel had split away from Zeiss Ikon.
So maybeearly Multiple layer coatings is that intermeddiate term

Just needs some simplicity.
Ian