That is interesting. I covered high school sports in Maryland (Frederick Co and west, although we would go into Carroll, Montgomery & Howard Co a little too) and I recall watching a kid play football for one team, starting a basketball season for the same team. Being kicked off the basketball team, and transferring schools and finishing the year at a rival school in the county, while leading them deep into the state playoffs.
I think that a lot of what Maryland (MPSSAA) does in high school sports would be great for the WPIAL and PIAA to embrace, but I always viewed Maryland's transfer and eligibility rules to be very lax.
What year was this?
If I remember correctly, if you moved to a new school with your legal guardians you were eligible immediately.
If you got special permission for whatever reason to attend a school when you didn't live in the district you had to sit out for 365 calendar days.
There was a 45 day rule if you transferred within the county but I can't remember the specifics.
I'll be honest, I despised the way Maryland operated high school sports. As a coach, you could barely do anything in the offseason without potentially breaking the rules. That's why AAU sports are gigantic in that state. From December till June, I couldn't have a football present at any workout that included more than 2 athletes. During the summer, if I wanted to have a football present at any workout, I needed to have a 7 on 7 scheduled with another team. Yet, I couldn't use my school name, school colors, uniforms, etc... I hope PA never even entertains these types of things.