This issue is no longer reproducible. If experiencing the described behavior, reach out to Esri Support Services as a reproduction case is needed for continued investigation.
解决办法
Add the following details for the code to work as expected when embedded in ArcGIS StoryMaps: '%' in width and 'px' in height next to the numbers.
Use the “Copy link” option from the sharing options in the Instant Apps template to embed in ArcGIS StoryMaps for expected results.