That's because the piece is not in fact by Thomas Tallis, a 16th c. church composer, but by Ralph Vaughan Williams, an early 20th c. secular feller
Heh, sorry I guess you misunderstood. I know that was written by Vaughan Williams. My point was the piece doesn't sound at all like Tallis' style to me. However, I haven't listened to THAT much Tallis so maybe that's why.
Actually I didn't misunderstand you

I just wanted to explain why you might be having the problem you describe. To clarify, my point is that if you want to find more music in the 'style' of Vaughan Willams's recontextualisation of a Thomas Tallis theme, you would find it in the works of VW, rather than those of TT, whose work merely provided a source fragment that VW completely transformed.
A contemporary analogy would perhaps be in a case where artist X remixes artist Y. If you particularly liked the remix of artist Y by artist X, you might not find that much joy trawling through Y's releases, being more likely to strike lucky with X's.