This is the worst and dirtiest ROM flash method I have ever seen. Without TDB you can have same (main) ROM on both systems. The release version can be different only, for example sys1: MIUI6 5.1.30 / sys2: MIUI6 5.2.6, just like the updater app procedure doing.
If you had CWM with TDB why didn't you keep it and flash the ROM via CWM recovery on sys2 for safely use two different ROM?
And what will you do next? The next update via updater app or via MiRecovery will overwrite your MIUIv5 on sys1.
You have had tons of questions regarding ROM update before, all of them have answered, but you have chosen the worst way by yourself.
Sent from my Mi2S / MIUI6
first of all, I just asked if was possible keep v5, that I have in sys 1, and pass to multi in sys 2 where I have sMiui whithout flash fastboot rom and you sayd to try flash multi zip whit cwm to overwrite smiui, just to try before flash fastboot metod if it doesn't work. I did it two times but the screen was stuck on mi logo first time and black screen the second time.
so I tryed it out of curiosity (via Updater) from sys 1 and it worked.
2) just did the same: via updater from sys 1 (where I haveV5) flashed installation package multi 5.2.6 xiaomi.eu and now still have V5 in sys 1 and V6 5.2.6 xiaomi.eu in sys 2 instead V6 5.1.30 xiaomi.eu
P:S: both times whithout any wipe!!!!!!!
Switched between the two several times whithout any problem, both rom work.
I always knew that whithout TDB you can have same rom and different release, I had already flash via fastboot way my phone many times!!! This is what surprised me using this method that I wanted to try out of curiosity and not because I thought it worked, just before use the fastboot way!!!
Then I chose this way just to see what was going on, before flash fastboot rom since via cwm had not worked. Even I did not think it would work but it did.
In the end also I still do not understand how it is possible but it works, or at least I do not see problems, I can call and all applications seem to work properly in both systems while having the V5 and V6 in one another, without cwm and tdb.
Now you tell me how it's possible!!!!!!!!!!