I don't think that's true. Many big companies contribute to FOSS in ways that aren't just to attempt to lock people in. Often it's because they use the software and don't want to maintain patches forever - everyone wins if things actually get fixed. Or even because they just want to be known as a good place to work.
Name one big tech company in the same monetary level, that doesn't contribute to FOSS without second intentions.
That describes how hands off MS was with Postgres committers ime a few years ago. Useful to house them to for helpful office hours too. We'll see how that holds up post HorizonDB