Basically as in the title, the saurus host requires three units worth of saurus, since I have those three in the pregame, can I deploy them as one unit of thirty instead of three of ten?
I would say that is between you and who you are playing against, but generally no. If you deploy them as 1 unit, then that is what they are and should not count as three for the purpose of battalion bonuses. Also it doesn't say three units worth of Saurus, as there is no upper limit on unit size, but three Saurus units (containing any number of models, but no less than 10 per unit). Hope this helps
It's a blurred line at the moment. Some players believe that the Warscroll/Unit entry is worded in a way that permits units of identical warscrolls to combine. Although I can see where they're coming from (and I also believe that it'd make gameplay that much more interesting), I don't think that their interpretation is the actual intent.
I dont think its a blurred line, It is a very clear "NO". The Zombies warscroll has the following rule: Shambling Horde: If two or more units of Zombies from your army are within 1" of each other in your hero phase, they can merge and become a single unit for the rest of the battle. if that was allowed for any unit, why on earth would it be listed as a rule?