Martin, don't you get about 35 ppm Ca from the mash? Additions will get that higher, no? Some is Ca is consumed in the mash, but how much? Where would AJ be at by adding 20 ppm Ca?
Some makes a little sense to me. British Ale strains would benefit from Ca to flocculate quickly, as that beer is at cellar temps and on cask needs to drop bright quickly. Lager yeasts have a long time at cold temps, so they will settle out with proteins via Stokes law, so the Ca is not as essential.
If there are detrimental factors from higher Ca and lager yeasts, hope that is covered in the article.