First time poster looking for some advice if you are willing.

Last year I installed new hardwood in the master bedroom and refinished the 2.5" hardwood in the hallway. The entire area was re-sanded and stained with Dura Seal Special Walnut 124. It turned out slightly blotchy (in retrospect I think I didn't "pop" the wood consistently enough is my guess). We stared long and hard at the blotchiness and decided to VERY LIGHTLY and quickly reapply some stain. Blotchiness was removed and wood became slightly darker.

FFWD 1 year: We opt to remove the carpet in the kids bedrooms (at the other end of the hall) and install 2.5" red oak flooring (same as in hall and master). I'd like to think I did a better job of sanding and popping. Job came out great. The issue is that the match with the hallway is well...noticeable.

Option #1: live with the results and clear coat it and be done. Pros: job looks great, we didn't want it any darker (in fact we wanted it lighter!). Cons: spoke to a pro about what I did last year and he had a heart attack saying you just can't re-stain, the pigment just sits there, chokes out the stuff underneath, etc, etc. It could end up too dark (not good).

Option #2: re-apply stain. Pros: if done right, it may get us the match we want. Cons: could make it too dark, could ruin a perfectly good job.

Here's a video that I took that I think does justice to the colour differences.

https://youtu.be/E4VvG2KqW9I

What do you guys think?

I think that you could use #2 steel wool to firmly buff off some of the stain from the darker boards to get a closer match. The stain isn't too far off between the two areas. You would need to use steel wool substitute if you use water-based finish because steel wool particles left on the floor will rust using water-based finish.
I always polish the stained floor before applying the first coat of finish to remove grain raise. The first coat of finish would need to be abraded, too, when it has dried, before the final coat.

Thank you for this and for the reminder to screen in between final coats of finish. The challenge is that the darker wood is the existing (it's also clear-coated).

I ended up putting a second quick coat on the new wood to try to bring it up a level in darkness. This seems to have worked but the new wood appears to have a pink hue to it that is not visible on the older wood. The dark stain on the older wood gives off a yellowness in lighter areas vs. a redish/pink on the newly installed wood. Is this something I'll have to live with? Is it possible that the reddishness will transform to yellow with age?

It is red oak but so is the older wood...stumped by this.

The pinks in the new wood will fade and the yellow will come out over time. This is why it is so hard for a perfect match when adding a new spot.