Google bias is certainly a possibility.
So Goggle could be presenting an unbalanced analysis, similar to the main article in this thread which ONLY presented studies against masks and didn’t acknowledge the many studies that support masks.
However, it does demonstrate that there is no shortage of studies claiming masks do not reduce blood oxygen levels.
So the reader if not already decided, can read through the studies and determine for themselves, which they want to believe.
I am suggesting the reader should do this study on himself.
Gitmo has done so and reports reduction. I intend to do it in a few days,