Pretty much. In this case, a lower output impedance makes transfering the signal form the amp to the IEM much easier, without hassle.
An amp is a really dumb device. Like a guy, it can't focus on two things at once, or at least, do two things right at once. Also, it always focus on the bigger thing. "Big = get my attention" kind of logic. The "things" in this scenario are loads (resistances/impedance). By itself, an amp has a real small thing to exclusively focus on, its output impedance. It will drive all of its attention (voltage) to it. When you show him a bigger load (headphone), it will shift its attention to this new huge thing. However, he will always focus also a little bit on its poor and lonely little output impedance, making him work on two things at once, hence bad (remember, it's like a guy). As it tries to drive two things, it will lose focus and mess with both, doing poorly. The trick here is to make either:
A -> The headphone load so much more interesting (making it BIG like the new Audeze) than the output impedance so the amp will almost exclusively focus on the headphones.
or...
B -> Make the output impedance boring and not interesting (making it small) so whatever else you show the amp (your IEM), it will exclusively focus on that.
And that's how an amp work.
(you get bonus points if you find all the innuendo in this post).