Streaming services generally use text fonts that are rendered on the client (using the system or user-specified font). Blu-rays use graphical fonts that could technically be any image at all, but are usually just pre-rendered text with a specified font, size and position. Technically they could use burnt-in subtitles if they wanted it to look consistent between streaming and disc versions, but that would cause problems with international releases.

So I imagine the Blu-rays will revert to the Franklin Gothic appearance.