To me, any question containing the phrase "what to look for" is clearly not a gear recommendation question. That doesn't mean every question that is not a gear recommendation question needs to include that phrase, but for me that is why I wouldn't personally vote to close What to look for when buying a digital piano for a beginner?
Other differences between the questions include:
- The open one is very specific. It mentions "digital piano", tells a little bit about the intended use, and even has specific talking points listed. The closed one is much more vague. It uses the words "keyboard" and "popular tunes" without any amplification of whether the asker is hoping to sound like Trent Reznor or Burt Bacharach (both authors of what could reasonably be considered "popular tunes").
- The open one is only about "what should I look for in a digital piano?" The closed one has an extraneous question that confuses things and the additional information in the closed question doesn't help with understanding the product goals the asker has. Personally I can't connect the desire to "...play few popular tunes in a year and play charts from musical theory sheets in three." with information on good keyboard options because I don't have a connection in my brain between how quickly one learns and what instrument one uses.
To me a good meta question on the closed question might be, "How can we help people who don't even know what kind of question to ask?" Some people come here with virtually no understanding of music, but they are here asking questions because they want to understand music, and I should think encouraging that would be something this community would like. Sadly, many of these askers get their questions closed pretty quickly and not always with comments that attempt to help. Even when comments are posted, the gap between commenter and naive asker is sometimes so large that the asker doesn't even understand the thrust of the comment (as in this case and my comment on the question, it would seem).