When you're getting colonized, I don't know if it really matters whether the colonizers honor their promises more or less. Consider the Maori, the gold standard for a colonized people who managed to get a full treaty with the British very early on, even securing representation in government in the mid-1800s. Are they meaningfully any better off as a result of these agreements, relative to other indigenous groups? Not really, and in recent times they even seem to have slid back on many important welfare and quality of life metrics, despite changes in NZ policies towards Maoris that should have had the opposite effect. Sure the Maori may have built up "trust" in the colonizers' treaties, but since they were an out-group it didn't affect their day-to-day interactions, so they didn't reap the benefits that go with being part of the high trust society.
My point is that in-group relations is not the same as out-group relations. High trust is about how you treat members of your in-group. Enslaving foreign people is most certainly a "low trust" move (how can I possibly enter an agreement with you when I know you might just show up one day and enslave me?) but it's fully possible and consistent for the perpetrator to belong to a high trust society.