For the conservation of your home, please make sure your contractor is using lime mortar, or at least "N" mortar, which is the next harder pre-made mortar mixes. Most contractors do not and they use a mortar mix with a high Portland cement content.

Before the 20th century most masonry mortar was a "quick lime" & sand mix. It never gets extremely hard or brittle. 19th century Baltimore bricks are not hard as they were not fired in a high temp kiln. This is esp true for days when they used wood or charcoal for the fire. The result is when the bricks and mortar wet, with weather, then freeze, the Portland cement mortar does not move nor does it absorb moisture, so the water in the brick freezes and the brick crumbles.

Item 2 is the use of machines to cut out the old mortar. For the side and back of a row house they can be used with care, but the 1/8" thick facade mortar joint will be cut out and a wider gap will be seen, as well as all the mistakes in cutting with a hand held grinder. Your facade is a weak place on the house. To get that very uniform look, the original facade has no bricks turned front -back showing the narrow end to the street. This means the front row of bricks is not tied to the row behind them. When the mortar joint fails water gets in and with freezing part of the facade can fall off.

I am re-pointing the mortar joints in my basement, and have spent time looking at youtube clips about the proper manner to repoint old lime mortar. It is slow and I do about a 3' square before I tire of it. But the effort is well worth the learning curve.