This specific update introduced several technical refinements and bug fixes that made it a "Gold Standard" for many professional artists:
Added the ability to export tilesets directly as sprite sheets. Aesprite_v1.2.40.7z
Fixed stylus and pen painting issues on Windows that occurred when a mouse was simultaneously plugged in. Why it's "Interesting" Aesprite_v1.2.40.7z
Many users continued to use version 1.2.40 even after the release of 1.3 because of its reliability for professional commissions. Aesprite_v1.2.40.7z
For a long period, 1.2.40 was the default "stable" version on Steam, while 1.3 was kept in the "beta" branch for testing.