Did anyone ever say B5 was going to be this group's first target?
And why can't B5 be situated in a convenient path for them?
The problem is the lack of warning combined with B5 having been purposely positioned to be in the middle of all of the known races (which makes sense for original dimplomatic meeting place mission).
B5 could have just happened to have been on their path.
*BUT* if they were probing for weakness in potential opponents all along the way, and had to pass through enough populated space to get to something as centrally located as B5 is said to be, then the Alliance should have had enough warning to get at least
some of the White Stars back into a defensive posture before they actually got to B5.
Now, if you want to speculate about reasons why it might make sense for them to have remained stealthy until they got to B5, then you can come up with some things. It's that it pretty much
requires throwing out what is said about their motivations and strategy in the episode. It doesn't make any sense for them to be stealthy unitl the get close to B5 IF they are actually using a recon in force to test the combat strength potential conquest targets.
IF, on the other hand, they know a whole lot about the B5 region and what is and has been going on there, even though nobody in this region has ever even heard of them before ...... Then it could make quite a bit of sense to specifically try to sneak up on B5 and take it out. As long as the fledgeling Alliance President and Council is on the station, that could be a good way to try to break up the Alliance so that the smaller members would become easier prey.