Looks like they tried fixing it again:
Updates to Team Fortress 2 and the Source Engine have been released. The updates will be applied automatically when your Steam client is restarted. The specific changes include:
Source Engine- Took a more aggressive approach to solving the exploit that would allow players to get underneath terrain in Team Fortress 2
- Fixed a regression with walking on terrain in Half-Life 2: Episode Two
SourceTV- Fixed building bone merge cache from dormant entities. Fixes weapons in SourceTV attached to wrong bones
- Pass over spectator UI and scoreboard in SourceTV mode, disabled/changed some VGUI elements
- ALT will switch to Auto-Director mode in SourceTV