As far as I've read, it's a matter of variable-sized buffers affecting sound generation in some synths, which is audible in patches that have, as quoted, "excessively fast and deep vibrato in the oscillators (i.e. not host automation)."
The other key quote from Urs is "Other types of patches don't seem to exhibit any issue".
It seems that using fixed size buffers solves it. I have not observed it myself (yet?), but if I had this issue, I'd probably enable fixed-size buffers in cases where it's audible, then measure whether that causes any significant latency, and try to compensate for that.
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The key question is whether you have encountered that problem. If you don't, there's no need to worry about it, other than perhaps out of technical curiosity.
If it was a common problem for making music, it would probably have been noticed and brought up more often, in 20 years of FL Studio hosting VST plugins.