PROJJSON prime_meridian as a value+unit object gives NaN from_greenwich

[jiayuasu]

I may be constructing this wrong, but when a PROJJSON prime_meridian.longitude is given as a value-with-unit object (the shape PROJ seems to emit for non-degree meridians) rather than a plain number, from_greenwich comes out NaN and the meridian offset seems to get dropped.

const proj4 = require('proj4'); // 2.20.9, wkt-parser 1.5.5
const json = {type:"GeographicCRS",name:"NTF (Paris)",datum:{type:"GeodeticReferenceFrame",name:"NTF (Paris)",ellipsoid:{name:"Clarke 1880 (IGN)",semi_major_axis:6378249.2,inverse_flattening:293.4660212936269},prime_meridian:{name:"Paris",longitude:{value:2.5969213,unit:{type:"AngularUnit",name:"grad",conversion_factor:0.015707963267949}}}},coordinate_system:{subtype:"ellipsoidal",axis:[{name:"Longitude",abbreviation:"lon",direction:"east",unit:"degree"},{name:"Latitude",abbreviation:"lat",direction:"north",unit:"degree"}]}};
console.log(new proj4.Proj(json).from_greenwich);        // NaN
console.log(proj4('EPSG:4326', json, [2.5, 48.5]));      // [2.5, 48.5]  (unchanged)

pyproj parses the same object and applies the shift:

from pyproj import CRS, Transformer
Transformer.from_crs("EPSG:4326", CRS.from_json_dict(json), always_xy=True).transform(2.5, 48.5)
# (0.16348, 48.50007)

A plain-number longitude (in degrees) seems to work fine, so it might be specific to the {value, unit} object form. At a glance transformPROJJSON.js (~lines 105/115) looks like it multiplies longitude by Math.PI/180 directly, which would explain the NaN if it's an object — but I'm not certain that's the right place. Is the value-with-unit form meant to be supported?

[ahocevar]

I don't see "longitude" supporting an object as value in the spec. Did you construct the projjson object yourself?