White space

This is a webtoon not a manga. A manga is traditionally drawn on paper and sold in physical copies so it's restricted to the amount of space on the page. A webtoon on the other hand is entirely digital there is no physical limit to the amount of space the artist uses. The white space is ultimately a design choice for the webtoon artist. Another thing to consider is webtoon are actually long vertical strip comics, technically the entire chapter is on one page. Uploaders on mangago cut up the strip to make more pages for their own reasons.

I see it as scene transitions or long ass pause. Some webtoons do go overboard with their pauses though.