But I'm using the Table of Contents check box in the Peripherals tools, not an FRT file. So I assumed that that auto-generated ToC would use some specific styles.
But I just found this in the .tex file:
\preptxfile\prepusfm\id FRT -- toc
\is Table de Matières \ip \ztoc |main\*\ip \postptxfile
\BodyColumns=2 % But ensure it goes back to the chosen Single/Double setting for the main body text
\useTOConefalse
\useTOCtwofalse
\useTOCthreetrue
\GenerateTOC[Table de Matières]{SHULct_Lect25-26_XXA_ptxp.toc}
And it does seem like it using \is for that title. However, the Space Before Factor doesn't seem to make any difference before the \is ToC title.