There is no separate file for isotope.js in this new release – all essentials are combined into multiple different dependency files together (only a few exceptions). If you are seeing an isotope.js loaded, then it is coming from a different plugin or the theme.
The scripts load based on this criteria:
– The noUI slider is only loaded if a custom field filter with a slider feature is used.
– The isotope is loaded if the isotopic layout is used, or either the masonry layout is used for the settings.
– The ploaroid gallery JS is only used when the polaroid layout is used for the live search results
I checked the source code of your site, and the smallest of the combined files is enqueued, which means these modules are not loaded, only the core plugin file – it is fully optimized 🙂