So I work at Oracle, but as an engineer. These are of course my own thoughts and I’m not representing OCI.
As far as I know, there’s no difference between any of the clouds as far as basic payment structure. If you don’t want to be locked in on a contract, you just give a credit card and pay the publicly posted rate. Exactly how are you a hostage in that position?
Portability between clouds assumes that you exclusively use the cloud provider as a sort of VPS host. Any service beyond that becomes a form of lock-in. YMMV, and this is of course true for all clouds.
Oracle is way past the point for that comment to be non-sensical. For any other company it'd be bizarre, but "hostage" doesn't even begin to describe Oracle customers.