The article is about allowing bandwidth restrictions in bytes/second that are larger than 2³²-1, not about how fast pf can filter packets.

I guess few people with faster ports felt the need to limit bandwidth for a service to something that’s that large.

FTA:

“OpenBSD's PF packet filter has long supported HFSC traffic shaping with the queue rules in pf.conf(5). However, an internal 32-bit limitation in the HFSC service curve structure (struct hfsc_sc) meant that bandwidth values were silently capped at approximately 4.29 Gbps, ” the maximum value of a u_int ".

With 10G, 25G, and 100G network interfaces now commonplace, OpenBSD devs making huge progress unlocking the kernel for SMP, and adding drivers for cards supporting some of these speeds, this limitation started to get in the way. Configuring bandwidth 10G on a queue would silently wrap around, producing incorrect and unpredictable scheduling behaviour.

A new patch widens the bandwidth fields in the kernel's HFSC scheduler from 32-bit to 64-bit integers, removing this bottleneck entirely.”