The full_crc32 option was introduced in MDEV-12026.

Any data file that was created while innodb_checksum_algorithm was full_crc32 or strict_full_crc32 will use a single CRC-32C that is computed over the entire page payload. Even if the innodb_checksum_algorithm is modified later, the same checksum will continue to be used. A special flag will be set in the FSP_SPACE_FLAGS in the first data page to indicate the new format of checksum and encryption/page_compressed.

For data files that were not created with full_crc32 or strict_full_crc32, the old rules will apply, and these values will be interpreted as crc32 or strict_crc32, respectively. The strict_ variant means that only the specified type of checksum algorithm will be allowed. The non-strict variant avoids crashes when upgrading from a dataset where innodb_checksum_algorithm=innodb had been used, but it weakens the page checksum, by accepting corrupted pages using a different checksum algorithm.