> Swap files have had the same performance characteristics as swap partitions for more than 20 years

I thought so too, then I benchmarked it on a (spinning rust) HDD and found it was significantly slower:

https://www.vidarholen.net/contents/blog/?p=1110

tl;dr: "In this test, using a swap file was surprisingly 50%+ slower than simply allocating a swap partition at the start of the drive, in spite of the low fragmentation and Linux’s bypass of the FS layer."