Sure, in some cases. But where is the Red-Hair Pirates in this?
p.s.
You make it sound as if the whole Red-Hair Pirates work together to form a kind of united haki
Nope it is not. Shanks does the wifi haki alone.
Yes, Mihawk did say only Shanks, but He also said only WB, and We all know that Mihawk came to help against entire WB Pirates,
We've also seen him mention Shanks, Blackbeard & Luffy when talking to Buggy,
In both cases, Mihawk is referring to Opposing these Factions, not a Duel against their Representatives,
For Loki's Case, i'm not saying Red-Hair Pirates Defeated him, but my stance is that We simply don't know what happened, it could have been Shanks alone cuz Loki challenged him to 1v1 Duel, it could be Shanks + Beckman similar to Garp/Sengoku vs Shiki cuz Loki was Destroying everything, it could be entire Crew to end the Fight quicker ... etc Oda never reveals how the Fights went exactly before the Flashback is shown (For example Sabo didn't collide with Admirals during Levely, also don't forget that Beckman, Roux & Yasopp have Higher than normal Bounties, that means They have their own Great Achievements)
As for Shanks Wifi Haki, Yes i do believe his Crew was Included but it doesn't mean it's them who were Unleashing Haki, it's still his Sole Haki but He used a Technique to include their Presence, just like you can learn to make your CoA cover more than just your Body, and you can learn to make your CoO cover more than just your Senses (Such as what Yasopp & Kata & Zunisha did before), i believe you can make your CoC cover more than just your Presence
So Ryokugyu only felt Power of Shanks CoC, but He felt it released out of entire Crew,
I'm not trying to De-Hype Shanks, anyone who read couple posts of mine about him knows that i think so highly of him (even more than most his Fans tbh, as i don't consider Roger or Joy Boy to be above him), but it's clear that Oda wants to Hype his entire Crew all together, so we can't ignore them & treat them like just any other Crew
Shanks might be a legend