In the past couple of weeks I have reported several times on problems for display and output of OpenType SVG fonts with Adobe InDesign CC2019:
It seems that there are two different spots to save the font resources in a PDF file. The Adobe PDF specification since PDF 1.4 (2001) were unclear in this regard.
Dietrich von Seggern reports in the Callas blog that the OpenType SVG fonts have been a topic at a recent ISO meeting on PDF 2.0. In the dated revision of ISO 32000-2, which is currently in the final voting process and is scheduled to be published in 2020, the situation is clarified.