Table 112 ("Entries in a Type 3 font dictionary") from the PDF 32000-1:2008 reference states that the value for "Encoding" can either be a name or a dictionary.
Under the value description it states:
(Required) An encoding dictionary whose Differences array shall specify the complete character encoding for this font (see 9.6.6 "Character Encoding").
The value description seems to indicate the only valid value is an dictionary, but it states in the type column that it can be either a name or a dictionary.
Are named encodings meant to be used as values for this field as well, or strictly encoding dictionaries?