The LEDs in the article are WS2812B LEDs that operate at 5v rather than 12v. 5v is a slightly more "normal" LED voltage, 12v strips are usually going little tricks like have 3 or LEDs in series and using that to get the required 12v drop.

With the WS2812B you're issue is that they operate on 5v logic for communications. 3v logic from a chip can _just about_ communicate with 5v devices. But you can't send the signal very far before the voltage drop stops communication. The cheat here is to use a single WS2812B LED as logic voltage converter. You put a resistor in line so it's operating at ~4v, give it a 3v logic signal it can understand, and it'll then talk down stream using ~4v logic, which you can then pump into normal 5v LEDs.

You can find detail of this little trick on hackaday[1]. But it's specific to WS2812B type LEDs that are really microcontrollers that happen to also put out light, rather than traditional dumb LEDs that have no smarts.

[1] https://hackaday.com/2017/01/20/cheating-at-5v-ws2812-contro...