I've seen this quite a bit and don't think it's bizarre at all. It makes sense if you want plusher carpet in your bedrooms and more wearable carpet on the stairs. I really like having the texture on the stairs and in the hall. It hides spots and makes a long strip of carpeting more interesting IMO.

I took a few pictures to try to show the hall/stair carpet we used and how it is near other floor surfaces. And here's my disclaimer... I just got back from a few days away for business travel, so it hasn't been vacuumed in several days! And IRL it doesn't show the foot prints / traffic pattern like it does in the photos.

The hall wall rug goes by 6 rooms with different floors: 4 carpeted bedrooms (each with different carpet) and 2 tiled hall baths. It might sound weird but it works - the colors and textures all look nice together, and most important, everyone got what they wanted for bedroom carpet and bathroom tile.

That yellow rug in the first room on the left is just a throw rug in DD's bathroom. (I should have moved it for the picture. The carpet looks good next to her tile.) At the end of the hall you can see DS's bedroom, which has completely different carpet than the hall -- much plusher and a different color.

{{!gwi}}

How it looks next to MB carpet:
{{!gwi}}

Stairs (not this orange IRL):
{{!gwi}}

We did that in our last house.

We had a solid beige freize in the main area and the steps were a pattern that complimented the beige. It had the same beige background with a soft neutral floral and leaf pattern.

We received many compliments on it.

Thanks. The idea is growing on me now I have actually seen it. What's that phrase - a picture is worth a thousand words?

I've done what your carpet guy is suggesting. I have a print carpet on my stairs and upper hallway and the same neutral carpet in the bedrooms off the hallway. Here are some pics:

Foyer/Staircase:

Hallway to bedroom transition:

karezz, I really like your stair/hall carpet! Very pretty.

I really like the look of placing a wood threshold in doorways to transition different carpet styles.

I love a pattern on the stairs, but it is best when you run it like a runner covering most of the step tops and stop on the first step down. I like seeing a little of the wood peeking out the sides. Then you do not need to tie it in anywhere else (although the color should complement nearby elements).
A solid color takes a beating more and will show its age sooner.

I agree with dianalo. If the staircase is a feature as you enter the home, it would look good to have some of the wood peaking out.