Verified as still present in the current release of 1607 … just for grins, I installed a fresh version of Win10Pro x86 v1607 on my test machine (an older HP Pavilion with an integrated 1394 port … ven1106/dev3044). 1394 works just fine (per limited testing). Sounds like this capability will disappear in the future, but still present for those that need it atm.
The debug/testsigning msg in the lower right corner reads:
Build 14393.rs1_release.160715_1616