As of now, this is a theoretical problem that was noticed during the review of JDK-8211294. See https://git.openjdk.java.net/jfx/pull/308.

As part of the initial implementation of TextFlow, a few package-scope methods were copied from Region. At least one follow-on fix, JDK-8120722, that modified those methods in Region was not propagated to TextFlow. It is not known whether this causes any actual problems, but it should be evaluated.