Yes, but this is the same kind of cost as, say, switching from an OO to a functional design, and we don't normally refer to "choosing to use OO" as "vendor lock

Yes, but this is the same kind of cost as, say, switching from an OO to a functional design, and we don't normally refer to "choosing to use OO" as "vendor lock-in". This phrase is normally reserved for use when there is a vendor that one must pay in order to continue to use a service, not merely cases where there is some difficulty or annoyance involved in changing something.