Why is this a surprise to anyone? Blizzard extensively advertised what patch level the Classic client was going to have. Compound that with the knowledge and experience from 15 years of WoW, the YEARS of folks who played Private Servers, and people are going clear Rag and Ony in greens.
If they released the game as the 1.0 version everything would be horribly unbalanced, they had to choose a patch and frankly picking the most “complete” patch of Pre-BC content with the most balancing and tweaking makes sense.
Did you expect Blizz to release the game with Pally Reckoning bug? Or the the Baron Geddon bomb pet glitch?