That does not appear to be correct.

https://github.com/Polymer/lit-html/wiki/How-it-Works#4-upda...

Excerpt:

update() simply iterates through each part and value (the parts array and values array are always the same length) and calls part.setvalue(v) for each part.

https://lit-html.polymer-project.org/guide

Excerpt:

Behind the scenes lit-html creates HTML <template> elements from your JavaScript templates and processes them so that it knows exactly where to insert and update the values from expressions.

This is very limited. You need to manually update DOM unless your updates are simple changes in values of expressions.