I believe those 3 companies have shown and demonstrated their competence and ability to deliver world class software. Huawei has not, at least yet. Whether that will ever happen remains to be seen.
Edit: To close04: No one, but you ever talked about Cisco.
This being said my main reason for being skeptic about HarmonyOS is that it's a v1.0. And just like almost all other v1.0s it has a lot to prove and improve.
Anyway, I think you moved the goal posts. You were implying they should not be included in the group to be sceptical about, rather than any kind of scale.