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.
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.
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.