Note the missing XContentFactory etc. I checked version 6.4.3 as well and this was missing too.
org.elasticsearch-6.5.4.common.xcontent directory:
.
├── LoggingDeprecationHandler.class
├── ObjectParserHelper.class
├── ParseFieldRegistry.class
├── StatusToXContentObject.class
├── UnknownNamedObjectException.class
├── XContentElasticsearchExtension.class
├── XContentHelper.class
├── XContentParserUtils.class
└── support
└── XContentMapValues.class