I have recently been wondering this exact same thing. Over the last 5 or so years of focusing solely on SPS and acros I always believed that Alk swings were the main cause of any problems that popped up. So... last year I ordered an Alkatronic to see if I could fix any potential issues with Alk swings.
Fast forward to today (7 months of Alk monitoring), I can firmly say that Alk swings were never the sole cause of issues for me, even though I thought they were. Alk is rock solid in my system, only like .2 or .3 over the course of a week. And I have not changed anything with my dosing regimen, which is 2 part on auto dosers.
Since adding the Alk monitor, I learning that I need to look elsewhere for what would cause issues with my SPS.
I've since added auto water changes to my system. The reason I did this was to simply up the frequency that water was being changed, and take myself out of the equation. Not that I was bad with husbandry, just not as perfect as I wanted to be. I also could not find any test that would lead me to a potential cause of issues.
I know this doesn't really answer the question, but it does (for me at least) confirm that Alk is often blamed when something else is at play. What will be interesting is if I can draw a correlation between any future SPS issues, and an Alk swing (if there is one or not).
And BTW, my corals have been growing and happy since the AWC addition. (No recent issues, fingers crossed).
TMB