The biggest reason I believe they release these packs for those begging for a 1.5.2 version to "tide them over" till 1.6.2. Elo did this with RP2 and 1.3 I believe, where she waited till 1.4 to release RP because of the changing in coding of minecraft. Soaryn has also said on multiple occasions that he wasn't going to release XyCraft for 1.5.x but re-wrote the whole mod for 1.6.x. FTB team had/has a large community and pleasing all of us is very hard. So FTB Team releasing these 3 packs between 1.4.7 and 1.6.2 for those of us who WANT to go ahead and play with the mods AND some new mechanics from 1.5.2 can. OR you could you know wait a little longer with the version you have now till the 1.6.x versions come out. Don't get upset for updating when if your a server owner you update when you didn't have to. I know a couple of servers they aren't being played a lot due to the fact that they are waiting for 1.6.x first. So in other words chill... don't fuss at the the team who supplied us with what we wanted but then said the maps are not compatible. It's like biting the hand feeding you.
I agree and that is the point I wanted to make that really its up to the individual what they want to do or what they feel is best for there servers community as a whole. Me as i said before in my opinion its better to wait for me and my server community.