Sure it won't double it overnight, but if we give people enough time to train (4-8 years?) then I think it would have a significant effect. Though this example is poor because the quantity of new brain surgeons is restricted by various regulations and agreements (so we'd also have to assume those went away).

If you look at an unregulated field like software I think it's pretty clear that the huge increase in demand from ~2008-2020 did result in a huge increase in supply.