Perhaps not. Sapwood is living wood. As a tree grows, it produces chemical byproducts, some toxic. A tree is, after all, a living chemical factory. Like all chemical plants, there's a waste disposal problem. The solution is to pack the innermost sapwood cell layer with the waste, thus turning it into non-living heartwood. A new layer of sapwood cells grows just under the bark to replace them.

These toxins are what makes heartwood more rot and bug resistant, although that varies by species. If by 'resins' you mean allergens, its quite likely that will be much less in sapwood.

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And now there was no doubt that the trees were really moving - moving in and out through one another as if in a complicated country dance. ('And I suppose,' thought Lucy, 'when trees dance, it must be a very, very country dance indeed.')

C.S. Lewis

I'm confused, I thought you said he's a bodhran player...

No, let's not beat that dead goat again. Seriously, let's not.

As for the flutes, I'd agree that if you like the Copley, his Delrin flutes are within your range. Burns is your best bet for a wooden flute, and a used one may pop up if someone sees this post. I also would highly recommend the WD Sweet Shannon flute, well within your range and the first flute I owned. Not really a Pratten style, but good volume and tone, and depending on your hands may be easier to play, especially with his ergonomic hole spacing (I mention this because you said you have issues playing your bamboo flute).

Also, absolutely keep an eye out for used flutes on eBay, Craigslist, etc. About a year ago I bought a keyless Lehart for a little over $500, and it's a fantastic flute. You can get lucky and get a good deal if you know what to look for.

If you're interested, I have a used Casey Burns ABW Folk flute I'd be willing to sell.
They are very good starter flutes.