An escritura is a public deed or title deed which is signed in front of a public official (ie the Notary) who is there to ensure that the transaction is conducted in good faith
As far as I am aware all property has an escritura and the transfer of a property cannot take place without one – you cannot just make one up.
I think what Gary is on about is that the builder has built a number of properties on a plot of land without first subdividing them – in which case it will not have a separate escritura – only one that covers all the properties on that plot of land.
This can cause major problems later on. For example if someone has a mortgage on the property (for example the developer) and defaults on the payments – then everyone involved will lose their property if the bank repossesses. This is a simple basic check that should have been carried out before any money was parted.
Therefore there is legally nothing to stop him signing the escritura – except for the fact the property doesnt have an exclusive one so this will be impossible to do. I think what you are getting mixed up with is a private contract which is a contract between two individuals that does not need the presence of a notary.