The developers did not find evidence of an ultrasound Touch ID, but Troughton-Smith said a sensor under the screen was still a possibility.
He tweeted: "I mentioned ultrasound, yes, but I searched for much, much more.
"There is no evidence whatsoever of any new kind of Touch ID."
Apple revealed its HomePod speaker, which rivals Amazon's Echo and Google's Home, this year.
Because the speaker will have to work with Apple's new phone, it contains references to some of the upcoming features in its code.
Yesterday, the two developers revealed that the iPhone 8 will have an edgeless display and infrared camera, allowing users to unlock their phone just by looking at it.
Rambo uncovered a potential "attention detection" feature in the code.
Rambo tweeted: "There's also a lot of new references to facial expression detection," along with the section of the code he was referring to.
Facial references include "mouthsmile", "mouthfrown" and "mouthpucker", which are likely to be linked to the rumoured facial recognition feature.
Troughton-Smith meanwhile discovered a "tap to wake" feature that would allow users to double-tap their screen to wake their device.
He tweeted: "It looks like the new iPhones might support 'tap to wake', much like Windows Phones/Lumias."
Troughton-Smith also revealed that the iPhone 8 could have an edgeless display, having been tipped off about another section of the code by Rambo.
He tweeted an image of the outline of the new iPhone, saying: "But wait, there's more: images of the new iPhone form-factor are also present. A lot of people at Apple are going to have a nasty Monday."
The findings come just days after a report suggested that the iPhone 8 will ship in late October, and will not be available in white.
