Overall, the full 6 stations seems like a bit of overkill but it may be what's necessary to make the extension both functional and politically palatable.
The High Tech station can be excluded from the count, it will only exist because it can be built for cheap in the rail corridor. Between Finch and Langstaff ("Bridge" station), that's a 7-km distance with at most 4 intermediate stations: Cummer, Steeles, Clark and Royal Orchard. 7 km / 5 intervals = 1.4 km average stop spacing. That spacing is wider than on any other subway stretch, except the Yonge line between Eglinton and Sheppard where the spacing is 2 km. If we look at the Sheppard line, that's 5.5 km / 4 intervals = 1.375 km.
Having each of the Cummer, Steeles, Clark and Royal Orchard stations built is not an overkill; the issue is whether Metrolinx can fund all of them.