The way they replaced the qtr panel is probably the best method short of using NOS or good donor pieces. The reproduction hardtop qtr panels are very good and will do the job provided you keep the upper section from the original convertible quarters.....which appears they did from the photos they posted of the restoration process.
Many dont realize but the wave exists in hard tops as well as convertibles but they are different amplitudes. If the inner wheel well was good, or replaced with a convertible wheel well then the hardtop quarter panel will deform slightly to conform and match up to the remaining upper portion of the original convertible quarter panel.
That is what I had to do to my car and it worked. I also had the other side to use as a reference and a profile gauge is you friend.
The bigger issue with the hardtop quarters is at the very back corner. The hardtop and convertibles are very different back at that spot so some custom metal fab is required. I ran into that issue myself. Probably why they hung a jacket over that spot in this photo.
Looks great after it was all painted so I would say they did the best job possible. Very nice work IMO...