There is a discrepancy between SE-0351 and SE-0363 in how anchorsMatchLineEndings
is defined
SE-0351
/// This anchor is equivalent to `^` in regex syntax when the `m` option
/// has been enabled or `anchorsMatchLineEndings(true)` has been called.
public static var startOfLine: Anchor { get }
SE-0363
This option applies only to anchors used in regex syntax. The anchors defined in RegexBuilder are specific about matching at the start/end of the input or the line, and therefore are not affected by this option.
Last time I checked the behavior defined in SE-0363 was not implemented.