On Chryslers we just replace the boot, but on most Hondas the inner cv joint has to be removed to pass the outer boot down to its joint. That's a lot of work and much more costly so we often replace the whole shaft. Doing so should not require an alignment just for that unless the mechanic has to unbolt the strut from the spindle. I haven't seen that new of a Honda to know what has to come apart but that strut-to-spindle connection is one of the critical adjustments on many front-wheel-drive cars, and it can not be placed back in proper alignment by eyeballing it. There is no means of adjusting that on many Japanese cars, but it can change enough from disassembling and reassembling it that it can affect a different critical adjustment called "toe". That's the way each front wheel is steering when the steering wheel is straight.
If that adjustment has to come apart, your mechanic should have stressed its importance and insisted on including the alignment in the repair estimate.
When doing any front end repairs, a conscientious mechanic will inspect the other steering and suspension parts for wear and looseness. This is REAL important to do on Fords twice a year since they're known for parts separating leading to loss of control and crashes, but it's a good idea to have that done once every year or two on other brands. Besides that, your mechanic will "read" the tire wear for signs of misalignment. There's actually three indicators that an alignment is needed. You can observe at any time whether the steering wheel is straight when driving on a straight road, and whether the car pulls to one side when you let go of the steering wheel. The third thing is tire wear patterns. Bad wear takes longer to show up but it's the main thing mechanics look at during the inspection. Your mechanic should have explained why he is recommending an alignment. You should also be aware that if both wheels are out-of-alignment in the right way, the car can still go straight, and the steering wheel can still be centered, but you'll see it in the tire wear. If your steering wheel is straight now, and tire wear is good, and the wheel is straight after the repair, you probably don't need an alignment but I'd check the wear patterns on the tires once or twice a month to be sure.