Because the updatepack works ONLY on the install.wim. boot.wim manipulation was never intended or implemented.
No conflicts.
And anyway, servicing windows 8.1/10 isn't fully supported under windows 7. Conversely, windows 7/8.1/10 images can be serviced under windows 10. Simply having and using the adk from a newer OS doesn't provide full support for servicing newer OS images relative to the host OS.