I using Jesse Friedl's jfFlickr and jfZenfolio publishing plugin (latest release) with Lightroom 5.5
I've been using the jfFlickr one for years, all my photos there were published and up to date
I started using jfZenfolio, published some pictures. I then notices that the photos I published in jfZenfolio now show up as "Modified Photos to Re-Publish" under jfFlickr
In fact you can see them showing up under jfFlickr as "Modified" one at a time as they get published to Zenfolio