The spider is not pressed down. The cone sits flat on the 9.25" landing on the 6-spoke 18" or on a super thick 8" spider pack; the next landing down is for an 8" spider so the cone is pressed down to meet the spider ID on a standard 8" 3 spider pack. When the re-cone is sat on the customers frame the spider sits up off of the glue landing; the SURROUND has to be pushed in a bit for the spider to rest flat on the landing. The offset is about ~6mm or so.
The surround compliance is not nearly enough to result in pulling the spider forward.
If the spider were pressed backward or pulled forward that would be an issue.