Following on from the discussion in #11430, the additional question of the serialization of font-style: oblique 14deg was raised.

Following the rule of "shortest serialization", there is an argument to made that font-style: oblique 14deg should serialize as font-style: oblique, as the spec states that font-style: oblique (with no angle given) should use an angle of 14 degrees:

[...] The lack of an <angle> represents 14deg. (Note that a font might internally provide its own mapping for "oblique", but the mapping within the font is disregarded.) [...] (https://drafts.csswg.org/css-fonts-4/#font-style-prop)

Whether or not this argument holds, the spec should be explicit if this behavior is expected.