I had a lot of angst when I was writing the fact sheets fior these two, particularly when canescens is gazetted as General Biosecurity Duty (previously noxious weed) in NSW and nodiflora is not. Here are my two draft fact sheets. I think I finally got it right. https://apps.lucidcentral.org/plants_se_nsw/text/entities/phyla_canescens.htm https://apps.lucidcentral.org/plants_se_nsw/text/entities/phyla_nodiflora.htm
I think they must have got that from Plantnet, which states that canescens leaves are up to 3 cm long and mentions calyx lobes as one of a number of distingushing features. I will add that to my fact sheets. Vicflora says the leaves can be up to 7.2 cm long, and Weeds of Australia Queensland Biosecurity Edition says the leaf length is 7.0 cmlong, though I suspect they copied that from Vicflora.
I collected a herbarium specimen of Phyla from Coolamon Ridge on 19 Feb 2019, located at 35 21 01.7 S, 149 01 25.7 E. If this is from the same location it's definitely Phyla canescens; the calyx lobes being much shorter than the calyx tube is a good defining character.