When multiple blocks apply to the same IP/target, and one (but not the others) is set to prohibit editing the user's own talk page, the user may still be able to edit.

See, for example: these blocks (log1, log2) – despite having talk page access disabled per the first block, the user was able to make this edit to their talk page.

Of course, this is undesired behavior – if any block that applies to a target prohibits editing own talk page, then that target should not be able to edit their own talk page.