Both. There's no set speeds, the cores will bounce around according to temps, boost, usage etc. Bios and windows are seperate and respond seperately, according to how fast its read. Speeds can change in milliseconds, 4.2 to 3.8 and back to 4.2. If Hwmonitor doesn't read the speed change when it happens, it'll just stay at 4.2.
Never been a fan of Hwmonitor, it was decent back when it was written, but there's too much changed, especially about how mobo's read, respond, addressing, speeds etc.
Hwmonitor reads one temp on my Z77 as 255°C, another temp as -125°C and my 12v rail as 8.23v. Not likely scenarios.