Yes, November 2018 - April 2019 is the prior 6 months. Not a lot of house selling going on usually. The majority of house sales are not within those months (at least in the US). A lot of it is regional (weather related) as well, but it's really mostly dictated by the school year. Most parents try to avoid moving their kids to a new school mid-year if they can help it and wait until school gets out to move.

https://www.zillow.com/sellers-guide/best-time-to-sell/

I feel like you're trying to say that house sales just stop, or come close to it, during this time. When the reality is it's more like a few % points drop in volume. If it took OP an extra week or three sell? Sure. But 6 months? Something else is wrong.