In pppoe daemon exist rate-limiter mechanism which allow not shape marked packets. Often this feature need for ISP which provide access to some IX or own resources.
As example, if we want provide access to 192.0.2.0/24 without rate limiting, then in this case we need add to pppoe config next
[shaper] fwmark=222 down-limiter=htb
and set rule for marking packets
iptables -t mangle -I PREROUTING -s 192.0.2.0/24 -j MARK --set-mark 222
We can set fwmark static or configurable via CLI.