Hi
OK so I have gone fenix 3 to 5 plus, and back now while my watch being fixed and each time there is a chance you will get the wrong steps end of day total.
If you have two fenix watches my suggestion is switch over start of the day, make the new watch the preferred one, that way post midnight all steps on that watch count towards your total.
Othwewise as example say you had a 15,000 daily target, if you do 8k on one watch, then switch watches, and do 9k on the new one, so hitting what 17,000, while both watches show you have hit the target, and both watches show in the weekly widget going forward you did, and even the garmin Connect app, and website shows you hit target.... POST midnight, some process runs server side at garmin that the excludes the non preferred watch from your steps total, and your back to 9k, and that 9k will be uneditable, and affect any targets you may have for days hitting steps....
I had hit my target for 184 days this year until my fenix 5 plus migration day, well tbc I did hit it that day as well, just not according to my stats...