Incremental image alignment decreases the original matches

[Ryuseiken]

Hello. I have tested "Incremental image alignment" in Metashape Pro 1.8.4, according to the user manual.

First, after confirming that "Keep key points" is checked in Preference dialog, I have added 5 images to the blank chunk, and ran "Align Photos." As a result, image C3_2 got 3097 total and 3032 valid matches with image C3_4, as shown in one of the attached images.

Then, I have added another 5 images to the chunk. Consequently, the chunk consisted of 10 images: 5 aligned and 5 non-aligned.

After that, I ran "Align Photos" without modifying the alignment settings. As a result, the number of total and valid matches between image C3_2 and image C3_4 were decreased to 1231 and 1171, respectively, as shown in another attached image.

So it seems like the matching are reset and retried among the originally existed images too.
Although it is mentioned in a past post that "Incremental image alignment" does not decrease the original tie points, I guess the above-described behavior can decrease the original tie points as a result of decreasing original matches.