When we doing rollback, MediaWiki generates a default summary:

Reverted edits by UserName (talk) to last version by UserName2

But in some wikis (nlwiki) summary by default is another:

Reverted edits by UserName (talk) to last version by [[user:UserName2|UserName2]]

When we doing rollback via site, ping to user UserName2 is suppressed, but If we do it via API, user receives ping.

See discussion: nlwiki => metawiki. I tested it in the Sandbox. Code of my tool is very simple:

$params = ['action' => 'rollback', 'title' => $page, 'user' => $user, 'token' => $token, 'utf8' => '1', 'format' => 'json'];
$client->makeOAuthCall($accessToken, $apiUrl, true, $params);