Akadama is volcanic clay, that is clay in a volcanic region- thus some of its properties.
Judy, akadma breaks dow, all clay products will break down. Means you need to repot on a schedule. My trees freeze thaw- have for years, I just repotted a number of trees (about 100 that were in Akadama-Pumice-Volcanic or in Clay King Premix) that were last repotted in 2005-2008. Now, I don't let my trees freeze down to the -0 F level, we do protect and provide heat to keep above 15 F, no real issues. Yes the akadama is not as highly structured as it was, but it certainly was still functional. SO may be the issue lies with the quality of the akadama used, the repotting regiment and perhaps if the soil is appropriately screened, etc.
Interesting conversation, I too am looking forward to the day that we have a good Akadama equivalent in the US. I buy enough that having it available is important to me.