It does seem to be a terribly ingenious way to go by converting the valve circuitry directly but of course AM sets never had DAB so even with the cleverly spaced out dial conversion I can't quite see the point-except as a novelty item to confuse future researchers perhaps
Maybe this is because getting the DAB station signal into various bits of equipment eg DVD or CD Recorders, Hi Fi Systems or just different rooms, is always big focus for me. At the onset of DAB little micro converters were on sale for a while but then rapidly disappeared. The options now are quite expensive, eg units designed for in-car use or a few stand-alone DAB Hi Fi Units, even more costly. I tend to source more or less the same cheapo portable DAB radios and wire them in via the earphone output. They have the controls on the front so they can be easily inset into other equipment as well. Battery Power consumption is not an issue as they aren't really so portable anymore.
Dave W