[~kvn] suggested it here:
https://github.com/openjdk/jdk/pull/27002#discussion_r2310320298

We will eventually use unified logging, and so it is important to collect prints on the same line into a stream, so we can print them at once. Even some multi-line prints may need to be gathered in a stream first. However, there are some cases where debug printing is helpful when it appears line-by-line, so it is easier to debug. So we'll have to decide case-by-case.