While you're waiting for the official line on support, I think it's worth looking at other issues around your question.
Why are you not keen on installing Elastic Search? If you are following the recommended support for HCM9.2 (higher frequency, lower impact upgrades - selective adoption), then you will want to be keeping relatively up-to-date with tools upgrades. As you do this, you'll notice that Elastic Search quickly becomes the only supported search platform. As I understand it, this is purely a back-end change in search provider rather than a change to the implementation within the application (in fact, I believe you currently have the opportunity to have both running concurrently from Tools 8.55.11).
This technology has been available for over a year now, so I would be pushing for it to be installed in place of SES.
Per the Elasticsearch home page on MOS (2205540.2): SES is supported in PeopleTools 8.54 and 8.55 only until April 30, 2018.
Please review the content on the Elasticsearch home page as there is alot of detail there about what is supported with each tools release. You will definitely need to apply HCM 9.2 app fixes in order to use elasticsearch. Per this doc on MOS (2181988.1), the Elasticsearch fixes for HCM 9.2 were delivered in Images 16, 17, and 18 but if you need to get fixes, you should do so from the latest image.
At a minimum you will need to apply PeopleTools 8.55.11 patch to use Elasticsearch, but if you are going to apply a patch, you might as well jump to PT 8.55.19 or the latest 8.55 tools patch..