Depending on which option you choose ('webtrees db' or 'genealogy/GEDCOM'), you always have only a part of the changes. Some changes are missing completely, like deletions or multiple changes to the same record.
You have two options at the 'recent changes' menu:
1) 'webtrees' -> timestamp in mysql db
2 ) 'genealogy/GEDCOM' -> CHAN tag in GEDCOM data
a) When you create an INDI, than you will see with both options the 'creation timestamp'.If the INDI is linked to a family, you will see with 'webtrees' also the change in FAM, but not with the GEDCOM option.
b) When you (or others) change this INDI now multiple times, you will see only the _last_ change in both options. Changes before that are not shown (neither when nor who has worked on the record before).
c) When you delete this INDI, than this change is in none of both options recorded. With 'webtrees' option you will see only the last change from a) or b) and with the GEDCOM option the INDI disappeared totally.
The behavior with the 'GEDCOM' option I can understand (it simply searches for the tag CHAN) and is ok in my opinion.
From the option 'webtrees' I would have expected that all changes are displayed in a complete history. However, in its current form it is better than nothing.