Aberrant iPhone Results

Recently I’ve noticed that iPhone tests return glitchy waterfalls, and I tend to not trust the results.

For example:

https://webpagetest.org/result/200902_08_8cd472300a9e4215c0b61acf9e92760d/

The waterfall starts on top of the labels, and the 0 second TBT seems suspicious considering that a test for this page run on a Moto G6 returns ~3 seconds of TBT.

Any thoughts on this?