This isn't strange at all, but rather an artifact of the nature of heat energy in a medium. Heat is the uncorrelated movement of particles that evens out to zero effective velocity. Temperature is the measure of the velocity magnitude of these individual particles. This is independent of the medium's density.

That's the best part of them sending two of them. It can't be a random error.

I'm just a layperson, but I'd suspect the research is sound.

I hate the telephone tag, livescience.com-type journalism. Instead, I'd love to read an abstract and methods. The research must talk about this in detail and explain how the conclusions are reached. It probably isn't too inaccessible.

I suspect that there may be many such measurements correlated between both probes taken against some other baseline signal or an observed return to the mean.