It seems these researchers don't know anything about actual maple syrup production.
Most of the world's maple syrup is produced within 100km around where I live and I have visited multiple production sites.
There is an accumulation of >100cm of snow every winter in the forests here.
In the spring, the snow melts slowly and keeps the soil drenched for weeks.
This is the time when maple water is collected and also the time when tree growth happens.
Even with a warming of multiple degrees and a reduction in precipitation, there will still be snow accumulation and drenched soil in the spring.
Anyway, a mature maple tree has roots deep enough to be able to catch water below the water table, even during a summer drought.
It can take as much as 80 years for a maple tree to be mature enough to be a good producer of maple water.
Starting a new plantation takes decades, stunted growth or not.
Whether it takes 80 or 120 years will not affect the market.
The important is the production levels of the existing trees.
What could affect maple syrup production is if gets hot quicker in the spring.
The maple trees produce only during the period in the spring when it freezes during the night and it
If, due to global warming, the spring weather goes quickly from "winter-like" to hot enough that it does not freeze at night, then the maple season would be shortened.
There is already a huge variation in production levels from year to year caused by the differences in spring temperature.