Here is the full post from David (founder of Intervals) explaining the Strava thing. Best way forward (not just for LeCoach but in general) is to get your activities from the source (garmin, wahoo, zwift etc).
Regarding your question: that’s not much of a problem. If you change the sync settings in intervals then future activities will come in. And for now, when you make a training plan you can just tell LeCoach for example in the goal field that even though there are no historic rides visible to him that you are an experienced cyclist doing xx hours per week. Also in the ‘starting hours target’ field you should override the 0 value with how many hours per week you’re currently training on average.
Then it’s all good!
See this screenshot for an example:
