When lowering the config value world-settings.default.ticks-per.hopper-transfer the setting does behave as intended, as in it will only actually push items every given ticks, however it doesn't seem to reduce the servers total load.

Timings:

At default setting (every 8 ticks): https://timings.spigotmc.org/?url=xafehufoqu

Setting set to 240 ticks: https://timings.spigotmc.org/?url=rotoqonuve

Hoppers still seem to be processed the same amount of times and the performance improvement, even though processing should be 1/30, is negligible.

I could upload a small test world that contains a farm with 1k hoppers if necessary.