If all of the mounting bolts are tight, any movement in the seats is likely to come from the recliner mechanism first, then from the adjusters be they manual or power.
The recliners have more tolerance built into them due to the fact they pivot on bushings, which are typically plastic. Power adjusters will be more prone to movement than manual because they are more complicated and have more pivot points.
It will all boil down to the luck of the draw. If you happen to get a seat that was built with components that are at the outer limits of the design specifications, it will have some slop in it. Based on my experience building OEM seats for the past 17 years, this only happens very occasionally.