Yes, and your example shows why.
Most deletions of answers are not motivated by the mathematical content of the post, yet instead by formal reasons, e.g., the answer-post is asks a new question, and thus should be a new question-post or maybe a comment; the answer-post tries to engage with other users, and should be a comment, instead; the answer-post continues an earlier post and should be an edit to the earlier post.
The last one is your case.
To decide this, no in-depth mathematical knowledge is needed. It is a formal check and can be carried out by a much broader group of users. To insist that it must only by done by experts in the field misses the point.
By analogy, if I, as instructor of a course, insist that the students hand in sheets with assigned homework only in an envelope that indicates their name and the course, and that they deposit it in the office of an administrative assistant, then it is reasonable for that administrative assistant to refuse loose sheets. To explain to them that they must not refuse the homework because it is perfectly correct and they are not qualified to judge this, simply misses the point.
Arguably it is overly rigid or even pointless to insist on the sheets being in an envelope, but that's neither here nor there, and in particular it is completely inappropriate to target the administrative assistant about it because they did not make that rule either.
To come back to the present situation, if you want to discuss the merits of insisting on an edit rather than a second post, then you should ask about that, not question the qualifications of those that correctly enforced an established rule.