Sure, having less padding increases I/O efficiency. I was just commenting on the author's apparent confusion as to why the padding is there in the first place.

Here is the full(er) quote:

  Postgres will happily add padding to the underlying data in order to make sure it is properly aligned at the physical layer. Having the data aligned ensures faster access time when retrieving pages from disk.

This might be misunderstood as "Postgres adds padding to speed-up disk I/O", which is the opposite of what actually happens. Padding slows-down I/O but speeds-up the CPU processing afterwards.

SQLite made the opposite tradeoff.