Thanks guys, I greatly appreciate your input... and I do feel better now.
The installers are here now and we just discussed the issue. Looks like we figured out a "better" way of installing the boards from here on out so that no sanding is "required". Instead of trying to get the butt-end seams to match perfectly and smoothly (requiring blend sanding), we are now going to add a very small bevel to all butt-ends, somewhat attempting to match the t&g bevels on the long sides. Adding small bevels at the butt-ends will provide a lot of "forgiveness" and thus any "steps" will not be too noticeable and no sanding needed. They will no longer be adding the staggered angled cuts or glue.
Previously, the installer's concept was to keep the seams tight, even and smooth. I suppose I should have been more on the ball myself and thought more about this before proceeding. I pretty much just let the installer go nuts without discussing it. Now looking back, I should have never agreed to any sanding, and should have communicated to the installer that it was not important to me to have perfect, nearly invisible seams. There's no right or wrong here, just a matter of preference, opinion, etc. The installer is excellent, I could never fault him, amazing general carpenter, but he's not a "specialist" at wood planking. I suppose a "specialist", a guy dealing with planking every single day, would have known not to spot sand.
So from this point on, we are going to bevel the butt-ends, no sanding... and as for the planking that's already been installed, the installer is going to go back and carefully cut bevels at the seams to match the new beveled seams we are now yielding with the installation from this point on. We already did some test cuts and it all seems to look good. He is able to match the bevels well enough. This new "bevel" idea was the installer's idea anyway, I think he already knew there was an issue with the sanding after we did a few rows yesterday, so this morning we both mutually agreed that we needed to "improve" our butt-end seam technique.
The sanding splotches exist on maybe 25% of the ceiling area, so it's not the end of the world. But the frustrating part, the splotches are right in the most "important" part of the ceiling, right over where the console will go, and it's an angled ceiling, so when you're mixing etc, the splotches will be right in view... and any important promotional photos of the studio will include these splotches too (though I suppose there's always Photoshop
).
But you guys have made me feel better, I will expect that over time these splotches will "blend in" better and perhaps not be as noticeable as they are to me now. Plus I can perhaps figure out a way to maybe hang a few things, bass traps etc, over the splotch area to cover a bit of it up. I originally wanted the ceiling as exposed as possible in this area just for maximum dosage of natural wood, but...
And yes, I am well aware that whenever starting a project, it's always wise to never START at the most important point in the room, because inevitably, you always make some degree of errors when first starting out and learn as you go. As a rule, whenever I do a project, I start in the least important spot, learn my lessons, then work my way over to the more important sections. In the case with this planked ceiling, the installer just happened to prefer to start in what was the most important section (he didn't know it and I failed to point it out), all the tools, scaffold etc just happened to be in that location, it was simply more convenient to start there, and I didn't really want to say, "hey, move all your stuff to the other side of the room because I'm afraid you may screw up this side which is more important". And the fact that the installer had already planked a few of the walls and it came out PERFECT gave me a lot of confidence... but what I failed to recognize, the wall work had no butt-end seams... the ceiling was the first phase of the project where butt-end seams were required.
That's the report FWIW. I'm gonna go back in there now and choke on sawdust for a bit, see what's going on in there. Hope this new beveled seam idea is going to work out well. What I do like about it is that it's going to add that much more texture and interest to the ceiling, the individual planks will be a little more defined now, etc. The installer is doing a great job at choosing random seam points, nice overlapping, very random, nice choice of planks, he's mixing them up nice, etc.