As described in the Oracle "Non-Standard Options" documentation, this HotSpot option turns on strict class-file format checks. For compatibility, this option is also supported by the OpenJ9 VM.
Oracle recommend that you use this flag when you are developing new code because stricter checks will become the default in future releases.
Note: You cannot use this setting in conjunction with -XX:+ClassRelationshipVerifier.
By default, strict format checks are disabled.