To help you gain a better idea of that concept of no - bias trimmer control - I once did up a review of a Uniden PC-687 Radio - their upgraded replacement to their PC66/68 series - which failed miserably and was only in production for a few years then dropped.
It's also when they introduced a DEDICATED 6-pin NEW connector requirement because they needed something to help sell their Bearcat (Or BEERCAN) Bluetooth handsets - 906. - the old 4 pin connector days seem to be gone in Unidens book.
Heres' a photo of the Final from that review effort...
To get you up to speed on this...
They use a Resistor / Divider network - meaning that they still do the Bias - only they pre-set the level because they find it works the best under all conditions they subject it to - so they feed using 8.2K with a filter cap and the bias is trapped from there and they place a 4.7K resistor ACROSS the bias line to drop it more than half it's voltage to about 3.0 ~ 3.2 volts. This is a dead giveaway to the type of MOSFET they use - close to the 520's biased threshold turn-on line.
That will work from the IRF-520 - but if you put in a 13N10 or something else like an ERF2030 - that might be TOO much bias voltage and it will latch on and blow because...
NOT OF A BAD SWR, but because it simply turned on with no signal - it turned on because the BIAS line was telling it to turn on - too much voltage.
If the signal was there, and that turned on, with the BIAS set too high, the MOSFET will conduct, yes, but too hard in it's non-linear (nearly full on Digital switch region) ruining the signal and even destroying the part in the process.
If that didn't destroy the part, it will place too much distorted (Spurried) output into a subsequent stage ( Read:Amplifier) and potentially damage that amp.
As you get acquainted with the site, look up some of the 13N10 and IRF520 reviews and Radios like the RCI 2547/Galaxy MOSFET conversion - you'll see where they encountered failures due to poor signal control from overly-volted bias on MOSFET's - even in-between types and Brands.