It’s Tulane (I could opt not to say it but someone could easily enough look back at my message history and figure it out). 
The registration information doesn’t go back far enough to capture any non-COVID years but would guess the 2016/17 data set wouldn’t have been impacted substantially. A student isn’t likely to have done 3-4 years of the program only to have COVID completely blow it up. I agree that the class starting Fall 2019, COVID could well have driven the steep(er) drop off from 68.
And we often talk about the attrition rate of the program but there’s been some statistics out there that ~50% of ALL college students change majors. Assuming that’s anywhere near an accurate statistic, Arch might be higher than average but not dramatically.
In any case I agree with what was said earlier about the programs being more than willing to sit with a prospective student to explain what the profession is and what it isn’t - and the different paths to licensure. Every college we visited we sat down with someone in the program and they were happy to do it. Virginia Tech we visited on a Saturday and they set up for a couple of 5th years to walk us around and answer questions.
If you haven’t done so already I might suggest reaching out to the prospective program for your student and ask to talk to a current MArch student (someone nearing the end of the program) - Q&A around the benefits or downside of going that path. Looking at the different curriculum’s my sense is that the intensity of the MArch isn’t substantially different than the BArch. You’re not spreading the 5 years of work over 7 years. If the hope is to get your student established in college life in a less stressful way and validate Arch is the path for them then the BA Arch/MArch may well do that!