@Yatin It technically qualifies as spam. However, for users with other contributions, it's better to remind/inform them of the requirement to provide disclosure of affiliation using a comment, IMO. If the user continues to not provide disclosure of affiliation (i.e. not editing and/or posting new content without disclosure), or if there are multiple posts without disclosure, then a flag is reasonable. That may be a spam flag, but is probably better as a custom flag with explanation.
Basically, it comes down to judging their intent, which is sometimes difficult. If the user is here to provide good answers which are helpful to future visitors, then we want to try to get them to modify their behavior to be within SE's rules. If they are here primarily to promote their thing, then we don't want them.