I am just reviewing the documentation and I think I have found some typos.
The PWM frequency must be the same for pins in the same timer group.
On the Core, the timer groups are D0/D1, A0/A1/RX/TX, A4/A5/A6/A7.
On the Photon, the timer groups are D0/D1/ C4 / C5, D2/D3/A4/A5, WKP, RX/TX.
On the P1, the timer groups are D0/D1/ C4/ C5, D2/D3/A4/A5/P1S0/P1S1, WKP, RX/TX.
On the Electron, the timer groups are D0/D1/ C4/ C5, D2/D3/A4/A5/B2/B3, WKP, RX/TX, B0/B1.
Should the pins in Bold C4 & C5 really be D4 & D5?