The point is that each serverless implementation is different enough that even if you are using the same feature, the cruft around that is different enough to provide an certain amount of lock in.
Sure and this is to be expected. It costs time and money to align yourself with someone else's implementation and unless your customers demand alignment (e.g. S3-compatible storage interfaces), you're probably not going bother.
Again, this comes down to cost-benefit calculations. If some companies find that proprietary feature X from cloud Y provides a bigger (perceived) return on investment than not using feature X, then they are likely to use it. If company X later shafts them, they have to swallow more costs to migrate away but hopefully (for them) they took this possibility into consideration when they made their original decision.
