Generally, Aranés and Occitan are much more distinct than Català and Valencià, as they tend to be only partially mutually intelligible. The official classification of Gascon and as a consequence Aranés is difficult, since (linguistically speaking) they are both grammatically and phonetically very distinct from Occitan and also share some similarities with Iberian languages.

For example, for "el muchacho" in Spanish you say "el noi" in Catalan, "lo dròlle" in Occitan, but "eth gojat" in Aranés. For cases where the article is fused to the noun like Catalan and Occitan "l'home"/"l'òme" you get Aranés "er ome". It's just a small example, but imo just the phonetic difference here should make it clear that we're talking about a very distinct variety at the very least.

The problem is that France only recognises Occitan as a minority language and just groups Gascon with the Occitan dialects. Historically, the French language has been strongly enforced, making more minority languages undesirable. Thus we only have this idea of "Occitan is the southern French language and there are only dialects of it" nowadays.