Totally agree, to me the coolest part is that the group rolls in and out with different folks all with different skill sets applicable to the song they are covering. They are super skilled. It just looks like they are always having a blast.
I watched a video how they practice and produce. They all go home with the original song and practice their parts. They then get together and do 1 or 2 takes for the final recording. Cool as ****. They are good musicians for sure.