Comment OP provided zero sources. This could be an online form where people can lie and say they are the other gender to feel better about themselves. Removing the chance of lying who got questioned could have also interpreted "heavier" as "fatter", not generally "bulkier".
Or they could be made up or have atrocious sample sizes and selection, as per usual with general polls.
If the ad is under a filtered domain, it will simply not load. If the ad is under the same domain as the site you are using (ex. Youtube) they will load just fine.
When the primary DNS is down, the secondary DNS will be used. This is the same regardless if PiHole is used or not, but is how DNS works.