I haven't heard that before. I "think" I may have installed my pushrod before installing the master cylinder, but I can't be sure. Not sure why the rod wouldn't go all the in until the retainer seats.
All you're trying to do replace the air with fluid. Here's a picture from when I did mine about 8 years ago. I bought the little kit from a parts store. Fill the reservoir with fuild and pump 2 inches about 20 times.
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