For the Explicit Block Mapping,why yamlbeans implements the key length < 128 ?

In the YAML Version 1.2 specification (http://yaml.org/spec/1.2/spec.html#id2798057),for the Explicit Block Mapping,having the following specifications:
If the “?” indicator is omitted, parsing needs to see past the implicit key, in the same way as in the single key: value pair flow mapping. Hence, such keys are subject to the same restrictions; they are limited to a single line and must not span more than 1024 Unicode characters.
why yamlbeans implements the key length < 128 ?
return length < 128 && (event.type == ALIAS || event.type == SCALAR && !analysis.empty && !analysis.multiline || checkEmptySequence() || checkEmptyMapping());