To me, it sounds quite impossible that there would be big differences in forgiveness of time, temperature and agitation between different manufacturers. This goes both ways around! Rollei claims that their kit is MORE forgiving, when they claim it can be used at almost any temperature. You claim the opposite from your experience. I claim that neither is true.

I'm sure your results are for some other reason.

You have some random error, or this is again one of the many Rollei problems. 5 second difference doesn't cause a disaster, it will cause a minor shift in overall density and contrast and a very minor shift in color balance / crossover. 30 second difference is considered 1 stop push/pull, thus 5 seconds equals to about 1/6 stop, a difference most people cannot see or even measure, no matter what.

So, the real problem is not the time, it can be a temperature problem (of 1 deg C or more), a mixing problem or a Rollei problem.

For temperature, there are a few cathes;
1) Make sure your FILM and TANK are at temperature before starting (a decent preheat, at least 5 minutes without prewet, preferably more, or a 2-stage prewet with carefully measured temperature)
2) Make sure your DEVELOPER is at correct temperature. Measure the developer, not only water bath.

If your process is not consistent, it's hard to say whether one process is more forgiving than other. After all, what the inconsistency is, it's randomness, and you can have good results by luck. Make your process consistent.