Basically non-existent. All of the flagship phones I've seen are 2x2 at most which caps out at ~800? Ish Mbps on wifi 5/6? Something like that? I don't have the numbers in front of me.

Simply: it's less important to see 1Gbps+ numbers on your mobile device. Many can't even process data that quickly, aside from maybe a speed test. So there's a point of diminishing returns where you're just eating your battery in order to process data as fast as possible, and it makes no observable difference to your online experience.

The main thing is that since wifi is half duplex, reducing the background noise on the WiFi, you'll get faster response times, because you're waiting less time for the wifi channel to clear so you can send/receive data. Lower ping = faster network response, which makes it feel faster. You only need 100-200 Mbps of bandwidth to satisfy most data needs for devices, and the only benefit to more bandwidth is when downloading files/apps/games, when you're simply waiting for the data to make it from the server to your device, and it's a large amount of data.

I only have 100mbps of internet bandwidth at home, and anytime I go to another location and use the WiFi, even if it has more bandwidth, it almost always feels more sluggish, because I've optimized everything I possibly can, within my network, to reduce response times for requests. This is most obvious with the 13th gen i7 I use for work. It's an incredibly responsive system, and I regularly need to take that system with me to go to work on a site (I work from home, with occasional on site visits required), and the sites I go to may have fiber which has significantly more bandwidth available, but lacks the optimizations I've implemented at home, and it still feels slower. Between the increased latency from a busier wireless network, and the lack of on-site DNS at many of the locations I go to, I notice the difference quite readily.

Keeping devices per ap low, and optimizing common sources of slowdowns like DNS response times, it's possible to make almost any "broadband" connection feel fast.