[Radio Wrangler]

The extra transformer gives you an extra pole of LC selctivity and because crystals have spurious responses, you rely on the LC filtration to cover for these, so that's good. Also the non-transformer version has that choke supplying DC bias to the driving anode connected in an asymmetric fashion, the extra transformer fixes the asymmetry. But this form of filte doesn't work without special crystals whether there is a transformer or not.

Dvid