With https://github.com/clojure/clojurescript/commit/8f38049d543b04b8da55029f140b6577e3ec245a in a situation illustrated below, code gen that previously involved .call has been optimized to avoid .call.
Note elem(attr,kids) in the following:
The previous commit that causes code gen with elem.call(null,attr,kids):
In the downstream Hoplon  target test environment, this appears to have differing semantics at runtime, with the elision of .call resulting in an error
Adding a bit of diagnostic code in Hoplon surrounding elem to print out what you get if you apply js-keys to it, and you will see that the SVGElement has call (as well as other fields associated with ClojureScript).
I suspect this is the result of Hoplon extending js/Element for its purposes , and this is why you can actually invoke it.
Given the above, a minimal repro of the issue:
Previously summoned Lurch: