I agree, I did a couple of hours on the 727 at bournemouth, again prior to a certain 1-11 check. I did some pretty shocking flying in the 727, but it went quite smoothly in the 1-11, I imagine though that if the sim check had been my first experience of a jet then I would have failed..I passed by the way.
It also gets you used to the cockpit, and whilst the basic tee is there, just the size, possible distractions and location of flap and trim etc are worth experiencing first hand.
I also told the assessor that I had done a couple of hours in the 727 prior to the assessment, the assessment does not change because of this, and I agree, it shows that you are really serious about getting this job. Also what is a couple of hours in a sim when compared to the cost of the CPL / IR plus ATPLs that you have already forked out on - a no brainer!