Spam Score is a metric created by different third party SEO softwares that explains how many spam websites are referring to a particular website.

However, spam score isn’t any official metric referred by Google (confirmed by John Muller in a reddit post) for improved ranking and you can safely ignore them.

Infact many SEO marketers quoted that, diavowing backlinks even the spammy one decreases their domain authority and ranking.

Hence, It is safe to keep the backlinks and not disavowing them unless and until any manual actions will not be triggered.