In the WaPo article, it's the DA who is saying that the request could be interpreted as subjective, not the Supreme Court justice. The relevant line in the concurrence:

> In my view, the defendant’s ambiguous and equivocal reference to a “lawyer dog” does not constitute an invocation of counsel that warrants termination of the interview and does not violate Edwards v. Arizona, 451 U.S. 477, 101 S.Ct. 1880, 68 L.Ed.2d 378 (1981).

"Equivocal" probably refers to Demesme saying "if y'all think I did it", but nonetheless it's hard for me to read the concurrence as anything other than a bad faith interpretation of his request for counsel.