From their website, it is mentioned that pictures deleted from computer will no longer be deleted from Google Photos.
It seems to be an evil way to force people to use exclusively the Google Photo web app.
Is there a workaround ?
I like to take high-speed pics so that Google Photo will generate an animated Gif, but afterwards, I deleted the unused photos from these series directly on my computer. I want to do this offline, not on their slow web app.