Yeah, that's true. Maybe it would be better to describe these as single unit SFH developments in contrast to the tract housing of new subdivisions.There are many true custom homes in Oakville, but there are also many that are not.
A lot of lots being sold as 'custom homes', are lots owned by developers. Many older bungalows south of the QEW have been owned by developers, renting out these spaces for the interim. When they are ready to redevelop, some actually go ahead and have designs done. They then sell the real estate with the permit drawings to Owners. Some will sell the project to Owners, and offer different packages - so there is some customization but it is customization from developer chosen options. So in many cases, the expressions that you see on buildings do not entirely reflect the Owners.
Always remember that developers and contractors are inclined to limit choices for clients as much as possible. The more choices there are, the more possibilities for delays.