I have found this to be the case. Besides that, editors know what they're looking for. If you send an article that is right on target, most of them will use it within an edition or two. So always send the article.
Some editors save the article for two or three weeks before they use it.
What I do is keep records of the people I send the articles to and send them another one in about a month. It takes very little time to send the article. This has gained more success than article announce groups. Fill in the brief application 2. Receive approval decision within 30 seconds 3.