I'm aware of that. I'm an EM for a large tech company that sells multiple enterprise SaaS product.
You're right that the lock in happens because of relationships, but most big enterprise SaaS companies have relationships with multiple vendors. My company relationships with AWS, Azure, and GCP and we're currently using products from all of them in different products. Even on my specific product we're using all three.
When you've already got those relationships, the lock in is more about switching costs. The time it takes to switch, the knowledge needed to train people internally on the differences after the switch, and the actual cost of the new service vs the old one.
With AI models the time to switch from OpenAI to Gemini is negligible and there's little retraining needed. If the Google models (now or in the future) are comparable in price and do a better job than OpenAI models, I don't see where the lock in is coming from.