The only time a workstation attempts to contact its secondary DNS is if the first is unavailable.
A little more on that statement. It depends entirely on the MS operating system and patch level you are running at. Some OS/patch will fail on a DNS error (record not found). Others will contact the secondary. Most try both at the same time. Literally.
Heck even to this day MS hasn't fixed the bug where a 98, NT, 2000, XP computer will query the secondary FIRST and never try again (well they fix it in some patch levels then break it again). Causes havoc with internal DNS/WINS servers replicating only every 12 hours or more. Clients are totally freaked out that changes to hostnames or netbios names don't work until the next day.
The moral of the story is don't believe anything you read or see with MS dns. Throw a sniffer on the wire and realize nothing is as it seems or documented by microsoft.