Not all mowers have one. I like using mine, but many around here swear against them.
They've been around for a long time. At least 20 years.
I've picked up on that, the clean ports having negative reviews. But for years I'd take my old mower to the driveway, have it running and squirt a stead stream aimed under the mower and flashing up into the running blaces and it cleaned it well.
I wish I knew when they first appeared. Thanks for you info.
jack ":-Dx