MySQL 5.6 row format changes when changing storage engine from MyISAM to InnoDB
Please note that you ran ALTER TABLE ... ENGINE=InnoDB; That is a full table rebuild whether you go from MyISAM to InnoDB, or InnoDB to InnoDB (known as the NULL ALTER).

Please note the paragraph from the MySQL 5.7 Docs on innodb_file_format:


  The innodb_file_format default value was changed to Barracuda in MySQL 5.7.
  
  The innodb_file_format setting is ignored when creating tables that use the DYNAMIC row format. A table created using the DYNAMIC row format always uses the Barracuda file format, regardless of the innodb_file_format setting. To use the COMPRESSED row format, innodb_file_format must be set to Barracuda.