Invitation email when creating an alert on an item will sometimes contain the list + Item title while on other cases will only include the item title

I was facing an issue reported by our customer. here are the current settings:-

1. we have team site inside sharepoint on-premises enterprise 2013.
2. when users creates alters on list items, and they specify other users inside the alert "Send Alerts to" section as follow:-

3. the users defined inside the "Send Alerts to" will receive and invitation email.
4. But the PROBLEM is that sometimes this invitation email subject will contain the List Name + Item Title. while on other lists the invitation email will only contain the item title. so the subject of the alert invitation email can be:-

An alert for 'ListTitle: ItemTitle' has been created 

OR

An alert for 'ItemTitle' has been created 

where in the first email subject it will contain the list title followed by the item title. while in the second email subject it will contain the item title only.

now i keep searching for this issue for around 2 days but could not indicate the reason. until today i have capture the first hint. now all our sub-sites facing this problem are created using a site template. where this site template contain 5 lists. now if users set an alert on an item inside the 5 lists which were added as part of the site template then the alert invitation email will contain both the ListTitle+ItemTitle. while if we create a new list specifically under a subsite (in other word the list is not part of the site template), then when users set an alert for an item inside this new list, then the invitation email subject will only include the item title...so can anyone adivce what is causing this confusion ??