I don't understand, why disperse the force? To make the war more protracted?
Not everyone is trying to win the war in the fastest possible time, certainly. Some people are just happy to defend the systems they care about - if the big groups take out the Titan threatening them, they won't move on to another system, they'll just get back to doing whatever they were doing before the Thargoids came. If the big groups do something else, they'll put in a small amount of effort to keep systems they like safe, then do other things the rest of the week.
But also not everyone is set up for every type of action. Someone who isn't practised at Thargoid combat and wants repair support from a friendly station is going to be hopping around Invasions - whether or not that's technically the most optimal way to win the war. Haulers need inhabited Alert or Invasion systems to work in and Thor has very few of those (and the counterstrike bonus doesn't matter either way). Because Thor is relatively constrained for Alerts,
containing it by stopping its Alerts and maybe knocking out the occasional Control is a very efficient use of time, even if there's no plan to destroy it yet.
"Indra while containing Thor" therefore has a small advantage over "Thor while containing Indra" that containment of Thor is much more cost-effective, so the
total time to defeat both Titans is probably slightly lower (at least under the new rules) doing it that way round, because Thor will add fewer new Controls while Indra is defeated than Indra would add while Thor is defeated.
If you want to keep Thor contained efficiently and make use of the bonus counterstrikes this week, Col 285 Sector LB-O c6-1 should be a good target: retaking that will also prevent an Alert next week, so you save two systems for the price of one.