If Another Driver has to Brake to Accommodate Your Merge, then You're Being Rude and Unsafe
I think a proper merge means entering traffic without forcing others to slow down because they have right of way. If someone has to brake after you merge, there wasn't enough space to merge in the first place. When this happens, you shouldn't feel entitled enough to assume that others should brake to accommodate you, especially since you're the one yielding to them. I've encountered so many drivers who treat yielding as "I can go and others will adjust for me," but this is just inconsiderate and unsafe behavior that disrupts the flow of traffic. When I merge, I always assume other cars will remain at their current speed and I wait for a space large enough so no one has to accommodate me.
Btw I'm not talking about zipper merges or stop-and-go traffic where alternating is expected. I'm strictly referring to situations where one party is yielding to another who has right of way.