Sounds to me that you got a story from your builder similar to the one I recieved when building my house in the PA. My builder said that they were not using Tyvek and that they were going to use caulking and strofoam the joints between the sheathing under the vinyl siding.They also stated that the Tyvek would make the house too tight. I did not agree and I decided on using Tyvek at an extra cost.
Looking up Tyvek,consult Dupont on the product,understanding dialysis and diffusion will also be a benefit to understand how the Tyvek product works.
As a plus,your builder most likely has a vapor barrier under the brick work and if they used styform sheets under the vinyl, it most likely has vapor barrier on the outside. I used this system on my last house without Tyvek wrap and was very satisfied.