Ok so skipping the introduction (adb install, dev.-options enable, etc.), which is prereq of course, it would mean:
I would also need some more research, how this differs from just disabling, but it somehow clear that the app is not completely gone from the system (like when you uninstall it). Otherwise bring back approach would mean adb (in normal mode) would have access to a store or so to actually re-install the app (+ within /system).
I think the easter egg app is unimportant enough to test. 
:/ $ pm uninstall --user 0 com.android.egg
Success
:/ $ pm uninstall com.android.egg
Failure [DELETE_FAILED_INTERNAL_ERROR]
## it is a system app:
:/ # pm list package -s | grep egg
package:com.android.egg
## and after uninstall that way it stays/still visible in:
:/ $ ls /system/app
...
EasterEgg
...
:/ $ cmd package install-existing com.android.egg
Package com.android.egg installed for user: 0
## the same as? 'pm install-existing --user 0 com.android.egg'
So it is somehow “gone” and not visible for you in your user context anymore, but not completely gone from the system. Also it would be interesting if it is a difference in regards of updates. Will an OTA bring the App back or is it like one stated for the disable approach and it will stay disabled. We somehow drift away from the initial topic. Maybe a forums admin should split, if needed a this message. 