NSTextAlignment was changed from nsUInteger to nsInteger, what's the reason for this change?

In MacOSX10.13, NSTextAlignment was defined as "typedef NS_ENUM(NSUInteger, NSTextAlignment)"

But in MacOSX10.15, it is defined as "typedef NS_ENUM(NSInteger, NSTextAlignment)"

So the type of NSTextAlignment has been changed from nsUInteger to nsInteger.

I am curious what is the reason behind this change.

Thank you!