Probably?

As always with sex: Communication is key.

Be an adult, use your words, don't expect mind reading, or assume that you can.

EDIT:

Also... what are the actual bounds of 'initiating sex'?

Do you mean... requesting penetrative insertion, by means of fondling the involved area, as foreplay, to be later uh, made more mechanically involved?

Or... is fondling genetalia itself, sex?

A guy can come from a hand job, a gal can come from being fingered.

If thats the case, thats what you mean... then sex has arguably, definitionally, already commenced.

I guess you also didn't specify what part is being fondled under the pants.

Generally, I'd say any under the pants action is a pretty clear sexual act, but othet people may not agree with that, to some extent.

Maybe grabbing a cupfull of ass is significantly different to a handful of cock or kitty, to some people.

Maybe tracing a line just barely under the pants, near the genitals, but not actually touching them... maybe that constitutes an actual sexual act, maybe its foreplay, maybe its nothing, for different people.

There are so many potential variables and things that people take for granted that each detail just works the same way for everybody, without actually explicitly discussing...

You have to actually use words, and stop being cutesy or embrarassed or forcefully assertive without words.