Huh, I would have thought the opposite. Companies at Figma size are easily able to hire talent to maintain a core part of their engineering stack. On the other hand, they retain no control of Citus decision making. Those tailwinds could easily have been headwinds if they went in a direction that did not suit Figma.
I think this is true for things higher up the "stack", but doesn't necessarily apply to tech like Postgres [and Citus, IMO].
The line separating "build in-house" vs "use OSS" exists, and it's at a different layer of the stack in every company. IMO, for most companies in 2024, the line puts Citus on the same side as Postgres.
FWIW, I would have assumed that Citus would be on the other end of the line, until I had to look into Citus for work for a similar reason that Figma did. You can pick and choose among the orthogonal ideas they implement that most cleanly apply to the present stage of your business, and I would've chosen to build things the same way they did (TBH, Figma's choices superficially appear to be 1:1 to Citus's choices).