Upvote:1
According to the OP's own link, "Britain began military preparations in late 1792 and declared that war was inevitable unless France gave up its conquests, notwithstanding French assurances they would not attack Holland or annex the Low Countries."
France felt that she needed the outposts that she had captured in (modern) Belgium to further her Revolution. Britain was opposed to any such French expansion, and France knew that war was inevitable. Over a century later, in 1914, Britain and Germany went to war for essentially the same reason.
Being the "revolutionary" country, France wanted to make the first "declaration" and strike the first blow.