Has the receiver software changed how it uses the hardware?

I recently upgraded to 2.3.9.112 .  I had been far behind, running 2.1.something.

Every since I've owned a Flex, I was able to set it up the way I set up most rigs for HF.  I had any extra preamp shut off and generally set the AGC control (which I treated as if it were RF receiver gain) to a lower level -- usually in the 30s or 40s.

Since upgrading, the rig seems to behave much differently.  It cannot be the hardware fundamentals.

For one thing, I have to turn the preamp all the way on to get decent receiver performance.  And, whether I noticed it before or not, the noise floor, at least as shown on the panadapter display, dropped when I increased preamplification.

This was not a mere rescaling either.  Actual signals seemed to be about as strong as they were before.  Preamplification now simply dropped the noise floor.  This improved the signal to noise ratio.  This is contrary to my experience of HF rigs.

Also different was how the ACG "RF Gain" control worked.   It seems to have no effect I can discern until I drop it to maybe "10" or even less on the SmartSDR provided scale.

I have gotten OK performance this way ,but it really bothers me.  If there is a good explanation for this, I would appreciate having it. 

Receiver performance is very important to me, especially on the low bands,  and how I have the Flex tuned now is nothing like what I historically have done with any rig, including this very one.

Have I overlooked something?