Is this a firmware, slicer, hardware or model issue?

I have a VCore 400 which is working fine, I mostly print usable stuff but for a change I purchased a design model to see how it would come out.

It didn't come out very well, it has this almost "fuzzy skin" going on, on the pictures it's exaggerated as it's zoomed in and under harsh light but you can clearly see what I mean.

I thought it could be Pressure Advance so I turned that off and re-printed the base but as you can see in one picture those two models are nearly identical so it's no PA.

If I print a Benchy it comes out really smooth, so I don't think it's cooling either. In fact I'm running a CPAP blower at minimum 45% and bridging at 75% so I haven't seen cooling issues after I tuned that initially.

As you can see in one picture, the upper part looks better and that's where the slicer slows down due to layer time being < 10 sec. So slower gives a better result, but I'm not running all that fast tbh, or at least I don't think I'm running so fast it should be a problem?

Printer is running a VzBot toolhead with Hextrudort & Goliath, electronics are Duet 6HC & 1LC toolboard. Nozzle is a 0.5mm.

Any help is greatly appreciated.