That means you were using the wrong link. I just downloaded both the ROC and TFT installer EXEs, entered my legacy CD keys, and used them to install the game on a new Windows 10 computer at the time of writing. The game client reports that it is patch 1.27.0.52240 on the menu.
https://us.battle.net/download/getLegacy?product=WAR3&locale=enUS&os=WIN
https://us.battle.net/download/getLegacy?product=W3XP&locale=enUS&os=WIN
These means that I am running a version of the game that will not be able to connect to Battle.net to play online, because it is an outdated version. However, this version of the game is fully feature complete, including the capacity to play custom campaigns, which the Reforged client (and the RoC and TFT clients that you would obtain through mainstream Blizzard links today) does not have.