You have to be very careful when using GIS files for such precise things as parcels and municipal boundaries.
In this case, it looks like Detroit made the boundary swing all the way to Wayburn's right-of-way line. It looks like this is too far to the east.
Grosse Pointe Park's assessor shows 4 tax records on Kercheval west of Wayburn:
South side of Kercheval--
14932 Kercheval [[x2) includes Shaw's Books
14938 Kercheval Greenspace Holdings
It does not include the St Vincent de Paul shop
https://www.google.com/maps/@42.3806...egqhHJG-5A!2e0
North side of Kercheval
14945 Kercheval
I'm assuming it is at least the first bay with the roll-up door of the Art's Liquor Store building. The westernmost door has the address 14933.
https://www.google.com/maps/@42.3806...egqhHJG-5A!2e0
Oh, and the yellow markings on the road usually denote gas utilities.
Grosse Pointe Park's charter says the boundary is " a point on the East line of the City of Detroit, said point being a distance at right angles of
two hundred [[200) feet more or less, of the East line of Alter Road, as extended;
thence northerly in a straight line and parallel to Alter Road to the place of
beginning."
So, there is a funky jog in this area.
Finally, the people on the west side Wayburn filed a lawsuit a number of years ago. Detroit claimed they were in Detroit for the purposes of the city's income tax, the homeowners thought otherwise. The homeowners prevailed.
http://www.leagle.com/decision/19814...ichApp321_1397
So, this isn't the first time this border has come into question.