First of all I would like to write that your tool is great. Really - I love it.
Now to the question. I observe that effective VO2max is possibly calculated for whole workout duration. This is OK for workouts like Long Run or BS but for workouts like intervals the VO2max value is a little bit missed. When I upload my activity (like intervals, hills or repetitions) I set the Active and Rest periods. Wouldn't it be better if you have calculated effective VO2max value from only Active periods?