Same here. It's a policy I personally don't disagree with, though I have no expertise on the subject. And it's also applied to humans.Yes, it's a soluble broad spectrum with no egg withholding period. It'll go in the water until there's none left, then I'll switch to probiotics formulated for poultry in the water for a week.
Sometimes a course of linco is followed by a course of clavulox, usually by injection, but it can also be ingested. This time, I doubt Christa will need clavulox. Apart from being a little lean, she doesn't appear to be unwell at all, and I've been spying on her for a week.
The vets are limited in what they can prescribe and how much and how often, because of regulations aiming to curtail the development of superbugs.
I looked it up and lincospectin also exists for chickens here, but no authorization for laying hens which is the case for most of the medications I've used, whether prescribed or picked by me. They just don't seem to have done the testing. And anyway since antibiotics are completely forbidden for commercial laying hens, I don't think they will ever test antibiotics just for backyard chickens.