Impossible. There would be a massive outrage on forums if that would be the case. Instead, only some modpacks are affected - and not even everybody using it. Vanilla client and default XVM config don't cause it.
My (last) guess is that if Hitlog overlaps with certain parts of interface (or other mods), it causes the issue. As Aslain said - chat window seem to be the most common cause.
Chat window is a text field, similar to XVM hitlog. I think if they are on top of each other Hitlog acts as "active text field" (similar to open chat) so esc, ctrl and tab work only for that text field instead the whole interface. Other mods (that use text fields) can be causing this too - damage logs, info panels, crosshair, zoom indicator, penetration indicator, etc. Of course, I'm only guessing. Moving XVM hitlog solved the issue for me completely.
Try replacing battleLabelsTemplates.xc and hitlog.xc with default XVM configs and see if it helps. If you still have issues, try default XVM config.