Steve, I found that to be the case. If it's not the one you want, then try saving in a new spot it may change the patches and pokemon. Last time I tried though, I hit my spread over and over but no matter what frame I tried (I used at least 6 different ones) and where I saved in the grass I always found a bidoof rather than my target. And yeah, it is very easy to have random advances or advances from the 128 step counter, so make sure you know what frame you are actually hitting, then you can attempt to adjust your journal flips and steps/turns accordingly.
Edit: When I did this I was not starting a chain, rather hitting my frame with the first patch I walked into. I successfully used that method to catch a swinub previously, but it did not work at all during the attempt I describe above.