Multithread with MultiPeakFit.xop functions?

I tried using Multihread with a wave assignment statement ala
Multithread DestWave = LorentzianFit(coefs,x)

but Igor is telling me LorentzianFit (and the other related functions) isn't thread safe. I cannot think of why that should be the case unless it's just an issue of actively labeling them threadsafe and it hasn't happened yet, or is it something about it being an XOP? Clearly it doesn't modify the coefs wave, so it seems like it should be okay.
They were written before (or maybe just about that same time as) threadsafe support was added to the XOP Toolkit. Making them threadsafe should be relatively trivial and a boon to mankind.

John Weeks
WaveMetrics, Inc.