what color are you staining? darker will hide the difference quite well

It looks like Paint grade rather than stain grade - could you paint it instead?

He should put a conditioner on it before staining, which will even things out when the stain is applied. And a darker, semi-opaque stain should help even more.

Finger jointed wood is NOT stain grade. Only paint grade.

If you want a stained handrail, you need to buy non-jointed solid stain grade wood. Your contractor knows this. If you specified stain grade in the contract...draw your own conclusions about the integrity of the person you hired.

Thanks for your feedback everyone.

1. Yes we are staining it with medium dark stain, not super dark.

2. Should a banister have multiple pieces like this? I thought banisters are one piece in each section.

3. Even if he uses a conditioner how does that get rid of the lines?

4. My contractor is saying this well known stair place in town provided the materials. Is he lying and if so how can you tell?

It is becoming increasingly more difficult (and expensive) to get oak handrails that are made from a single, non-jointed piece of wood. I've had experiences where I've done a special order specifying non-jointed wood and ended up rejecting and reordering the rail because I kept getting sent jointed material. The last time I ordered was about 1-1/2 years ago and I got what I wanted. The lumber store could supply pieces up to 16' long and the cost -- based on profile and beefiness -- ranged from about $8/ft to almost $20/ft. I wouldn't be surprised if it was much more expensive in this post-covid world. I can't say if your contractor is lying. It may simply be that the supply of unjointed material is non-existent at the moment.

As for the conditioner, it won't get rid of the lines, but you will get less contrast between those jointed pieces when the stain is applied, and the darkness of the stain will help hide the actual joint. It won't be invisible, but it could be made significantly less noticeable. I'm not saying you should be happy about this, but your supply options for higher quality may be limited depending on where you live and what is happening with suppliers.

You will always see the lines. I had a door once, that came with finger jointed trim. Used conditioner, and a walnut stain. Showed and looked awful, we tore them off and replaced them, in just a couple of days. There is nothing wrong with finger jointed banister or trim, it just paint grade, not stain grade. I would either paint it, or ask to have it replaced.