Is a new ZZ Top record a "ZZ Top" record?

Since around the time of El Loco (and possibly Deguello) ZZ Top has had outside musicans contribute, both musically and creatively, to their albums. These musicans are, with a few exceptions, not credited for their work. Excluding Eliminator, which has a relatively well known issue of major contributions coming from an uncredited producer (enough info on that for a blog entry by itself), Afterburner all the way through to Mescalero likely feature varying degrees of uncredited players. I would be very surprised to find out that Dusty is actually the one playing all those keyboards and synthesizers on "I Got the Message" and "Doubleback".

But the purpose of this writing is not to speculate on who played what and how much this or that person contributed to a track, but rather to address the apparent decrease in the band working as a consise, united and creative force. Around the time of Deguello Dusty and Frank, tired of being second tier to Billy, requested to be treated equally with regard to writing credits for each song. Henceforth each song was attributed to Gibbons/Hill/Beard. And it stayed that way until Antenna, where all songs except four were attributed to the band (four were credited solely to Billy). With each subsequent album however there are less attributed to the three and more to Billy and individuals working in the studio (soundmen, producers, etc.). Mescalero had only two tracks (if you count the Japanese bonus song) attributed to the actual band members.

Now I don't really believe that Dusty and Frank contributed to every song on El Loco or Afterburner or Recycler - my point is they are likely becoming less and less interested in ZZ Top, as a viable entity anyway. It seems that Billy still actively writes and certainly records, as evident through his work with other artists. As previously mentioned he likely has 40 to 50 songs in various stages of completion. However Dusty and Frank seem to show little interest in being in the studio and recording. And with 1) Billy being the only writer, and 2) the propensity of so many other people to play instruments on their albums, just how much is a new ZZ Top record really a "ZZ Top" record? Just how wide is the line between a Billy solo album and a ZZ Top album? Was Mescalero a Billy solo album?

I'm likely overthinking it, as a big fan tends to do. The band has probably always operated this way to some degree since the very beginning, and the process is just continuing. Still I would rather see a lot of Gibbons/Hill/Beard than a little.