reduction may make the transition more difficult in the long term.

This is the only part that isn’t obviously true. Of course, this is a question of fact to be decided by evidence, but here’s my speculation:

Given the size of the population, it’s clear that there will be some people who fall in either direction. Some people will find a gradual transition easier, some will be hindered by the possibility. I’m inclined to believe that it’d make things easier for more people than harder, but I have no basis of evidence to make that claim. It occurs to me that a general push to reduce meat consumption will also likely move the Overton window towards veganism, which would make large-scale vegan goals easier to achieve.

Generally, when society at large is as far removed from a position as it is with veganism, advocating for a half-measure will tend to help the cause rather than hurt it. Veganism requires changing the minds of the entire world, and getting people acclimated to the idea that we eat too much meat will likely help with that.

LMK if I wasn’t able to answer your question, or if you want to ask another one.