I don't hear any 'strange tuning' in my JH13 FP's bass. I've used my HD800, T50RP Paradox, and HD600 for comparative reference (awaiting delivery of the UERM, though). The JH13 does seem to have a gently elevated sub bass and (lat, wide band) midbass (lift) lift.. I find the JH13's tuning to generally follow the Olive-Welti reference curve.
Hmmm.... I'm too skint to buy a CIEM at the moment, but previously owned UM's Miracle, and I really liked it overall, but found that the bass was fabulous at times, and rather 'elusive' at others (incidentally, it was being driven properly, by a DX100).
I dislike bass-ramped, and generally favour as close-to-neutral response as possible, but a subtly & smoothly boosted sub-bass (not mid-bass!) might suit me quite well.
I have heard that, broadly-speaking, the Miracle is 'similar' to the JH13 FP, so it remains on my list of (eventual) potential replacements for the Miracles I was forced to sell.
This Roxanne looks rather appealing, too. Sorry, very appealing, but if it's a ludicrous bass monster approaching the JH16, then I won't be even the slightest bit interested