Ikea has been running buyback and resale programs in various markets, so yeah, it's a real thing and not just speculation. The specifics vary by location though. In some places they've had a dedicated secondhand marketplace where you can sell items back, and they handle the logistics. The pricing is usually based on the original price and condition of the piece - don't expect to get anywhere close to what you paid, but it's better than watching something sit in your garage.
The tricky part is that this isn't uniformly rolled out everywhere. Some countries and regions have full programs set up, while others are still in pilot phases or don't have it at all yet. Your best bet is to check the Ikea website or app for your specific country and see if they mention a buyback or secondhand furniture section. If it's available where you are, they'll usually have details about which items qualify, what condition they need to be in, and how the valuation works.
One thing to keep in mind - the resale value tends to be pretty modest, especially for well-used pieces. If your furniture is in solid condition and maybe a few years old rather than ancient, you might actually get decent money. But if it's got damage or you're hoping to recoup like half the original cost, you're probably going to be disappointed. It's more about the convenience of not having to deal with strangers on Facebook than making back serious cash.