asAs it turns out, pv is the perfect tool here. At (at least pv 1.6.0). with With the -l (line mode) flag, -L limits become lines.
simpleSimple proofs:
1k 0:00:10 [99.6 /s] [ <=> ``` ```seq 0 10000|pv -l -L1k > /dev/null 10k 0:00:09 [1.03k/s] [ <=> seq 0 1000|pv -l -L100 > /dev/null 1k 0:00:10 [99.6 /s] [ <=> seq 0 10000|pv -l -L1k > /dev/null 10k 0:00:09 [1.03k/s] [ <=>