Yes, that's about 2Mbps, which is what YouTube's servers detect as the possible bandwidth between you and the server. YouTube CAN technically playback 4K video at something low like 20Mbps, but I can't see how it can do it at 2Mbps. The Network Activity line is the actual throughput of the data at any moment. YouTube may only download segments of a video, so it may be zero if it has already fully downloaded the segment and isn't ready to download the next. It may also not need to download more to refill the buffer yet. Mine is zero nearly all the time. 41KBps (bytes) is certainly not enough to carry usable high-res/quality video or keep up a full buffer. (I can't find anything to explain why this is just a quantity (KB) rather than a rate (KBps).)
I watched on mine, with a 600Mbps fiber line and YT varied showing I had about 128Mbps to 320Mbps, and Network Activity would be 10 to 12MB every 30 seconds or so. The only thing I can think of is that YT is actually sending you a stream that is much more highly compressed than what I'm getting, so even though it's still technically 4K60, the quality is lower. (YouTube converts uploaded videos and stores them in multiple resolutions with different codecs and quality levels to meet the needs of devices with different processing power and decoding capabilities and bandwidth.) If you actually viewed it on a 4K display side by side with a different machine that had a higher bandwidth connection and a newer CPU/GPU, you would be able to see the difference in quality, more artifacts and pixelation, but since the video player is downscaling it to fit into the resolution of the web page (or monitor when in full screen), many of the artifacts may not be visible. You could probably play it at 1080p or even 720p and not even notice any difference on that person's screen, or it could be even better since it's not going through so many conversions or having to be downscaled so severely.
Your neighbor is not getting 20Mbps. As I said, he may be paying for "up to 20Mbps" with DSL or wireless, but those services very often don't come near the maximum theoretical rate, and the providers are perfectly happy to keep charging for a high speed even when they know you can't get it. DSL is dependent on distance from the central office and quality of the copper lines. They'll sell you service that could make 20Mbps based on the distance, but the line quality may only manage 5Mbps, and if you don't complain, they won't do anything. (Business-class DSL services and early consumer DSL used to actually send a tech to test the line quality before the contract was set. Self-install DSL never had that.) DSL is often also highly oversubscribed, but that doesn't generally result in a lower speed all day long. Wireless service is also highly variable based on distance and oversubscription, and providers aren't going to blanket a rural area with a large number of nodes to ensure everybody gets a strong signal and that there's enough backhaul bandwidth.