Vectorworks 2017 introduced a change to the plant spacing. in the past your plant spacing was a specific number and that was it. Now, plant spacing can be a specific number or it can be “Best Fit.” The idea of best fit is that Vectorworks will try to put as many plants as it can using the spacing that you have specified, but it will always place plant start click and at the end click. As well as that, Vectorworks added the option to have the row spacing different from the plant spacing.
There is some great protected information here that is only available to paying subscribers. You must be an active paying subscriber to see it, but you can Subscribe here.