No -you do not need to install tiger ( os 10.4.x ) to run catalyst v4.
v4 has been tested on 10.3.3 and 10.3.9 - and hopefully will work on these.
10.3.9 is recommended - though will all the changes - there are no guarantees.
At this time - there are no features that are exclusive to 10.4.x
In the future there may be more stuff that only works on 10.4.x