Amazon has certainly done similar things in the past, but we can't know for sure without more data.
In the last twelve years, I've seen Amazon accused of all kinds of things, sometimes rightly, sometimes not. We never get enough data to know much until long after the fact.
My past faves:
"Kindle Scout isn't an Amazon program. It's a scam." It was an actual Amazon program, not a scam.
"Amazon is lowering our royalties to 50%." That rumor came about because 50% showed as an additional royalty point very briefly. A number of people believed this was an accidental revelation of a sinister Amazon plan. Others thought there would be a new 50% tier for people who wanted to be in KU and sell wide. (Some even thought that a good idea and started making plans to pivot into the 50% bracket.) Actually, the 50% was just someone inadvertently plugging in the royalty rate for Amazon imprints into the KDP dashboard. That was years ago, and the royalties haven't changed.
When it comes to Amazon, sometimes, we just have to wait for clarity.
