I'd think that the issues you'd encounter with a Japanese bowl (porosity, thermal transference) would be similar in a western-style raku vessel... assuming, of course, that there was nothing toxic in the glaze.
I've related this story before about a "food safe" non-toxic labeled product from one major manufacturer that I was wanting to use. I called to talk to their tech support folks to get an answer about any lead being in the product, since I make food wares and the FDA laws require that I know about that potential fact.. I got told by the people I first got sent to ... nope... none in there. But from talking to them and asking questions, I became well aware that I knew well more about technical ceramics than they did. These were their "tech support staff" that 99% of potters calling them would get. I kept asking for someone further up the technical "food chain". After a few layers and people who clearly could not answer a real techniocal enquiry, I finally asked them if they had a ceramic engineer type person on their staff. They said they did. I asked to talk to him. In about 1 minute or less I had my answer. Yup... lead in there. Those products are still sold by that company as "food safe".
It also jibes with my experience trying to track down similar information at another company. I was shuttled through about five layers of reps and technicians, and they finally referred me to an 'external expert' (basically another potter who used the glazes). I walked away no better informed than when I started.
It would boggle my mind that a company develop a cadmium based glaze (or lead) even in a frit, and call their product 'food-safe'... But that story of yours makes it clear that all assumptions are unwise here. I guess I'd better- at minimum- send this information to the customer and get his acknowledgement that he understands.