The term latency is usually used in audio to designate an initial delay. The correct term for your observation is, obviously, decay. For instance, TG334 was always mentioned to have that kind of behavior, and that one is an all ba iem, so bass decay has nothing to do with "coherency" between dynamic and ba drivers being put together.
However, I don't notice that said decay in bass. To me, compared to full sized headphones, the K3003 is pretty light and tight in the bass area.
When you compare it with BA based phones there's something to take into account. I found out that BA drivers, in general, have a hard time in giving an accurate bass response, usually, being light in that area, too fast, somehow unnatural, that being the reason why manufacturers started putting together hybrid IEMs. One can easily see how the BA based IEM market evolves: for achieving an accurate bass response they have to put several drivers to handle the bass (sometimes 4!). That was never a problem with dynamic drivers. OTOH we are very much used to hear dynamic drivers, and I'm referring to speakers and full sized headphones. BA is the new kid on the block and to me and my ears, they have the least natural sound, always sounding in their specific way, a bit compressed. So yes, I think it's a better idea to compare K3003's bass response with that of full sized HPs or the IE800 and the results you already have after comparing them are revealing. There's no 'coherency'/'latency' issue linked to the hybrid nature of these IEMs.