Any large project will involve initial work, testing, and revisions with more testing.
During initial testing in particular, it is better to group any issues that are found together, and submit them all at once. There are several reasons for that.
Tracking the changes that need to be made is easier. Quite often, more than one issue has the same base issue. When that base issue is corrected, several apparent issues all disappear. Finally, it makes the best use of the resources available.
We have a couple of customers who have the habit of sending each issue found individually. This greatly increases the chances that something will be missed. If ten separate reports are made in a short period of time, there is a greater one of them will be missed, then if one report with 10 issues is sent.
Also, when it comes time to address the issues, they can be organized, and an efficient approach formulated. When trying to address many individual reports of issues, it usually means that whoever is working on them ends up jumping from one point, to another, and then back again. The end result is usually an increase in the time and effort required to get to the end goal.
Much better, to send a consolidated list. This can be used by those doing the changes as a checklist. For those doing the testing, it can be used as an acceptance list. This list can, and quite often, will grow as other things are added.
In the final stages, when there is just a few discreet issues to be addressed, then individual reports start to make sense. In the early stages, fewer reports, encompassing more issues, will lead to a quicker and more complete resolution.