to personally give us his first hand account
It’s beferish in Rav Miller’s Sefer. Please stop being mevaze him with.
And it is correct that there is no inherent contradiction between Rav Miller’s beferish position on girls getting married straight out of Beis Yaakov (if not earlier) and the letter to R”Y signed. You unfortunately have a bad habit of keeping to put words in the R”Y mouths, which they never signed to in the letter.
You still have NEVER addressed why the age gap wasn’t a problem 100 or 200 or 300 years ago. My point is they had population growth + age gap (even larger than today) and never addressed this issue as a problem causing people to remain unmarried. Considering they had the same factors as today, to an even greater extent, and not the problem we have today — it would seem reasonable to observe that perhaps the alleged cause is perhaps not the root cause.