I don't know that I'd call it market timing. It doesn't happen every year, but it's a trend that's been recognized for a long time. I've never done it, but I know someone who's followed it for years (with a few tweaks) with some impressive results. Also, 5-10% in precious metal is a pretty standard hedge.
https://www.cnbc.com/2019/04/30/sell-in-may-and-go-away-maybe-not-this-year.html
An investor putting $10,000 into the S&P 500 between May 1 and Oct. 31, 1950 to the present would have $4,138, an astonishing loss of $5,862.
An investor putting $10,000 into the S&P 500 from Nov. 1 to April 20 over the same time period would have a gain of $2,836,350.
That is not a typo. We are talking about a gain of $2,836,350, versus a loss of $5,862.