Script wont show hidden element when 'hidden' class is removed

I have the following function:

function submitForCorrection() {
    try {
        $("#uploadSpinner").removeClass("hidden");
        setTimeout(function() {}, 100);
        SubmitForm('BoqReviewForm',
            'boqReviewTable',
            '@Url.Action("PostBoqFlags", "ProjectAuthority")',
            '@Url.Action("GetBoqReview", "ProjectAuthority")',
            function() { showNotification('Correction requested.', 'success'); },
            null,
            'Requesting correction. Please wait',
            false);
    } finally {
        $("#uploadSpinner").addClass("hidden");
    }
}

The SubmitForm call is rather timeous, hence me wanting to show a 'spinner' while it executes. Yet it's as if my

$("#uploadSpinner").removeClass("hidden");

line of code is totally ignored.

I know the spinner is in the correct place, because if I put a breakpoint on the removeClass line and manually remove the hidden class in Chrome dev tools, the spinner shows up exactly where I want it.

I've added the setTimeout(function() {}, 100); in the vain hope that removing the hidden class may take some time, and I wanted to avoid the SubmitForm call executing before the spinner is visible.

Why is my code behaving as if the removeClass isn't even there?