No, they were administering beta carotene and looking at conversion rates. They saw an association of those SNPs with a lower conversion rate (not "no conversion"). The SNPs provide a plausible explanation of lower conversion rates (though there are many other plausible explanations).

What this has to do with vitamin A actual deficiency (VAD, which is very very low in developed countries like the UK) isn't clear. There is no indication that those with the SNPs were VAD.

They suggest that people with those common SNPs may benefit by increased pre formed vitamin A intake in countries where VAD is common. They may, they may not. VAD is a very complex problem that is tied to the host of generally poor living conditions in poor countries.