What's a "completion of comprise"?

Comprise is a verb, according to dictionaries. Even legal dictionaries seem to give it as a verb:

= The whole comprises the parts; the parts compose the whole.

Law Insider

In this case comprise has been used (quite arbitrarily, and without definition or justification) as a noun that embraces any or all of the parts that comprise the legal contract.

The phrases “entire completion” and “entire completion” emphasise that payment is only required on completion of all parts. The agreement is that you only get paid if you do all the job.

Reference to substantial performance as a mitigation of the all parts condition admits the possibility of staged payments in relation to work done. The agreement is that you get paid parts of the total sum for parts of the job.

The prose about the garage merely illustrates these two approaches to the contract. Why such simple concepts have to be dressed up with such obscurity, distortion of usual English usage and solecism (build = built?) is beyond this simple correspondent.