For non-webwork interactives, that is controlled by code in `lti_iframe_resizer.js`
That is added to pages with the `lti-iframe-resizer` template.
There are a couple different tiers of includes added to HTML files. In `<xsl:template match="*" mode="standalone-page">`, standalone pages get the stuff in `$file-wrap-basic-head-cache`. Either that needs to get changed to `$file-wrap-simple-head-cache` (looks like most of that would be good to have) or, `lti-iframe-resizer` needs to get added to what is in the basic-head-cache (and removed from the tiers that build on that.