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" Im concerned about it impacting structural integrity of the brick?"

Brick should be fine if care is taken.

"also, will it be able to match the existing mortar?"

That is a big who knows as it will depend on the mortar and the care the bricky uses in the mix.

Thanks for answering

The concern is that they’re not being careful and causing damage to the brick as they do the grindout. Not sure if I’m overreacting but it doesn’t look like they care about not grinding into brick. Worried about long term impact on brick integrity

Brick is not structural and hasn't been for over 100 years. It's heavy wallpaper, that's all. You could smash a car through a brick cavity wall and not hit the actually supportive stud wall behind it, and the house would be in zero danger structurally. Your concern is not founded in reality.

Im not concerned agout the brick holding the house together. I’m concerned about the structural integrity of the brick itself. Nobody wants to pay hundreds of thousands on a new house that has cracking and crumbling brick.

Not a concern founded in reality. Brick is one of the most durable materials that exists. It lasts for centuries. Brick that crumbles was brick that someone got the bright idea to seal, then sealed in moisture, and a freeze thaw cycle spalled it. Don't seal brick. Cracking brick is incorrectly supported brick.