yes very correct. Pascal cards will auto boost to higher clock due to GPU Boost 3.0 , leaving very low headroom for overclock.
But few people knows how GPU Boost 3.0 works actually.
This is a gtx 1080 founder card showing how GPU Boost 3.0 at stock.
(clock frequency and voltage used)
1) there are several temp breakpoints (43c , 51C , 57C , 63C , 68C etc ) where the GPU will underclock by 12.5mhz each time the thermal breakpoint is met ,
most probably to protect the GPU from overheating i presume.
That is the reason why anyone with a pascal card will see their clock and voltage fluctuating up and down during gaming and might even experienced micro stuttering fps drop
2) u can see the below my stock gtx 1080 (no OC) start from 1898mhz and drop till 1835mhz @ 67C under 99%load ( temp could be higher if i stress test longer )
3) So what i do is
UNDERVOLT my card @0.90v and choose my highest stable clock @1911mhz .
I get a constant 1911mhz @ 0.90v and 7c lower temp becos of the lower voltage used.
No more micro stuttering and unnecessary fps drop.
p/s : undervolting your GPU should give you a free performance boost compare to Stock .