Looks like a lot of fucked 2-stroke chrome bore engines that have been ported.
A lot of that is due to the gas port hole being drilled after the bore was plated.
The chrome is cracked, and partially lifted when drilled.
The hot gasses finish the job, and peels the chrome back.
Now, one way to get around that would be to drill the hole before plating, chamfer the hole on the inside, then plate it, but I doubt any barrel manufacture would do it.
There are ways to chamfer small holes that intersect other holes, so that isn't a large issue.
But fitting the barrel to an adapter, then drilling the gas port, before plating the bore would be expensive.
On race engines (2-strokes), after modifying a chrome bore cylinder, I send them off to be re-plated.