It's sort of bizarre. If your goal is to reduce your divorce risk, and you can't/won't marry a virgin, then marry a woman with 5-9 past sexual partners.
I think it's important to allow for the possibility that the person analyzing the data is wrong. Here is something from the beginning of the source you linked:
A while after putting up my first post of subject of promiscuity and divorce risk, I was contacted by an individual who wished to analyse the data further. That individual, whom I shall call INTREPID, was able to analyse several cycles of data from the National Survey of Family Growth with regard to the promiscuity effect on the risk of divorce.
As far as I'm aware the data that has been obtained is not available anywhere in the published literature. I'm not a statistician and cannot vouch for the veracity of the data but I believe the analysis was done truthfully and without bias.
I want to publicly thank INTREPID for performing the task. I've had access to the findings for a while and have decided not to post them till now so that no trace could be linked to INTREPID. (The other reason was that I lost access to the account which contained the data and only recently was able to gain access to it)
INTREPID provided a report on his findings which I reproduce in full below.
Now, "INTREPID" might know what they are doing, but there is no way to know. No explanation is given for how the data was analyzed. What if "INTREPID" made a mistake?
It does indeed seem "bizarre" that women with 10-20 pre-marital sexual partners should have a lower "Pct. of 1st time marriages ending in divorce/separation" than women with 1 pre-marital sexual partners (which I assume in most cases would be the man they end up marrying, unless pre-marital sexual partners means pre-marital sexual partners other than the husband), or 2 pre-marital sexual partners.
Here is something that is off to me, if you look at Chart 2 which was also made by "INTREPID", and which has "2006/08 NSFG data" as the source women who have 10-20 non-marital sexual partners have an around ~50% on the "Pct. of 1st time marriages ending in divorce/separation" axis. However, from the same 2006/08 NSFG data on Chart 3, women who've had 10-20 pre-marital sexual partners have a 27.5% on the "Pct. of 1st time marriages ending in divorce/separation" axis.
Something about this is wrong. Assuming pre-marital sexual partners = sexual partners before the first marriage, and non-marital sexual partners = sexual partners before first marriage + all other non-marital sexual partners (so for example partners after a possible divorce, or maybe affairs, whatever), for any given woman, pre-marital sexual partners should be <= non-marital sexual partners, right? So the 10-20 women from Chart 3 should translate into 10-20 or 21+ women from Chart 2, no? So how does it happen that the 10-20 women from Chart 3 have a lower "Pct. of 1st time marriages ending in divorce/separation" than the 10-20 or the 21+ women from Chart 2?
Now maybe the vertical axis of Chart 3 was supposed to be different from the vertical axis of Chart 2, as is implied here:
For an even further revelation, I create Chart 3 which improves upon the horizontal axis as well as the vertical one. The vertical axis is the same as in Chart 2 and looks at the rate of first marriages ending in divorce (same outcome measure that Teachman looked at). But the horizontal axis now groups women by their count of pre‐marital sexual partners as opposed to lifetime non‐marital sex partners:
But the label on the vertical axis on Chart 2 and Chart 3 is the same. Maybe this is a mistake, or maybe the improvement was in numbers going up in increments of 5% rather than 10%.