Crop growing speeds

Yes, crops grow at different speeds and have different tolerances to cold temperatures. This is unrelated to the purpose of the calculator to which you link.

The calculator highlights how many food units can be produced (total and per laborer) in an ideal growing year for any given crop with a particular sized field. Also given that pestilence can ruin fields in an area for a particular crop, it is important that fields be crop agnostic. So it helps you create fields that are a good geometry for the available land.

That said, most years are not ideal. If you're doing things right, you should either be bumping up against your food quota during harvest time or preemptively squirreling food away in your trading post(s). In a fair year, your bean crops may be completely harvested to ideal quantities and when the pumpkin harvest comes along some are left to die on the vine due to your quotas. In a year where temperatures dive early, you could easily loose half your bean harvest, and be saved by your squash and pumpkins. The vagaries of weather are outside the scope of that calculator. Growing a variety of crops is a good way to cope with what the game throws your way.