The layouts do rely heavily on ACF, especially Repeater fields. By the time a site is handed off to me for development at our agency, the design is set–any pages that require specific layout have been specifically designed, so I know exactly what to build. The design process that leads up to that is very involved, so it’s extremely rare that a designer wants major changes during the design Q/A phase at the end of development–usually it’s just typeface adjustments and small changes to layout. I also try and build everything to be as flexible as possible (within reason), and try and to keep everything I consider “content” in WordPress so it’s editable: All the images and nearly all of the text you see on that site is user-editable from the backend.
Beyond that, if anyone starts suggesting major changes once we’re deep into development I just get grumpy and start talking about “timelines” and “budget” and “tradeoffs” and usually that quiets them down.