2010 blower speed changes

So my very first question here. 2010 Tundra, I noticed this year in the first 40 degree morning that when I started out I had the heat wide open,but for some reason the fan speed all the way up, did not really match the preasure out of the upper vents, this is my second going into winter so I might not be familiar with it. Anyway so I played with it today and this is what I found and need to know if its normal and why. Speed selector all the way to high, temp selector all the way cold, functioning properly, air is blast and seems to be matching the speed of the selector, now then as I move the temp selector gradually to hot I noticed at the mid way point not much change but going all the way hot the air speed slows way down, from the top vents, not sure about the feet vents. It does not sound like the speed changes the air just goes somewheres else. If you have a 2010 with manuel controls check it out for me, see if yours does the same, remember speed on high, temp on cold, mode top and bottom then gradually move the temp to hot and see if the speed diminishes some what.

 

I will toss out a guess of the blend door for hot and cold not functioning properly. The system uses a lot of plastic gears, motors and doors/flaps to direct air flow and blend hot and cold.

Probably need to either remove the HVAC box from the dash, tear it down and repair/replace the broken component, or replace the box with a new one.

I hope the issue is more simple, and imagine someone with firsthand experience will chime in.

 

Checked a 2011 it does the same, so its probably not an issue or defect, just wanna know why Toyota would design this to diminish air speed when the temp selector is turned all the way hot

 

Must admit I am kinda surprised, but my 2012 behaves exactly the same way. I have the airflow set mostly if not all to the floor/defrost when using heat, so I guess I've never noticed before.

So either it's normal, or all three of ours have an issue