Well, I have a 50% half-match with a 2nd cousin once removed (I am 2nd cousins with his mother).
See X chromosome comparison below from 23andMe:
View attachment 10921
A and B were sisters.
A had a daughter C and B had a son W (1st cousins)
C had a son V and W had a daughter D (2nd cousins)
D had a son U.
V and U exhibit the above situation (their X chromosomes half-matching for half their length).
A and B both have the same pair of X chromosomes. Say X1 from their father and X2 from their mother.
C got X3 from her father and (say) X1 from her mother A.
Let's assume, for the sake of argument, that W also got X1 through his mother B (50% chance).
Let's also assume, that C passed X1 to her son V (50% chance). W would pass his single X-chromosome X1 to his daughter D anyway.
D, having X1 from her father and (say) X4 from her mother, had a 50% chance to pass X1 to her son U.
This means that was a 1/8 = 12.5% probability that the same X-chromosome would pass to V and U.
It appears this is what happened here + recombination by A, B, C, and D.