True but remember that whilst the R7 1700 is fantastic value for people who need the cores, an i9-9900K is clocked around 50% higher (all core boost). The R7 1700 can be overclocked of course to maybe halve that gap.
Yep. there is a difference, but considering you can build an entire PC with the R7 1700, 16GB RAM, a 500GB NVMe SSD, an a decent GPU etc. for ~£500 that difference start to make it look like pee poor value unless you *need* the Intel. Also as others have said, you literally can type 37x or 38x in the multiplier in the BIOS and not even touch anything else and you have an all-core boost of 3800MHz, with almost no effort, so you've narrowed the gap spent nothing extra.
If you compare it against the CPU at around the same cost then the 9400F seems to be excellent value, but then if you are buying on a budget you end up with less for your money not more.