Texas Tech does not run a spread offense, they run air-raid. There is a big difference in the type of schemes that an air-raid team runs and a more conventional spread team uses. Plays like mesh and shallow cross are designed to attack man-to-man, but they rely heavily on 5 and 6 man protections, which are suceptible to the zone blitz.
Most college teams run ONE type of coverage 75% of the time and mix in some zone blitzes. USC is just one example, they run a version of under/eagle defense and play man free, with the ss free vs regular sets almost all the time, and when they don't, their zone blitzing. They still run other coverages, but rarely.
The game always spot-drops into zones, where in reality, most teams run more of a match-up concept, with defenders responsible for receivers in specific areas, not to oversimplify. Now days, only pro teams exclusively spot drop, because their athletes can cover the necessary ground and they can run more coverages. But even in the pros, spot dropping is going by the wayside.
Because the game just spot drops into zones that are related to the defenders alignment, this further complicates the defense. The whole idea about zone coverage is to cover certain zones on the field, not the defender dropping back x amount of steps etc. A hook/curl zone is a specific part of the field, and if a defender has that assignment vs the pass, it shouldn't matter where he aligns, that is his zone in a spot dropping scheme.
One more thing and then I'll shut up. Some of the coverage schemes in the game just aren't coordinated with the fronts and when the offense gets into non-regular type sets, with the weird spot-dropping zones, it leaves large gaps of green, leading to easy completions. A good defensive structure is designed back-to front, coverage first, because the zone scheme determines what kind of front you can align in and still be fundamentally sound vs the run and pass.