You must be in the Southern Hemisphere if the grower says a Clemenules will fruit in "May-Jul".

You have found the graft union on each in your pictures.

That won't identify the rootstock. There is actually a range of growth rates and sizes, not just a Standard or Dwarf rootstock. If it isn't identified, all growers I've seen will sell a Standard with an actual trunk and the first branches around 24" above the ground. Dwarf will be sold with branches starting just above the graft, usually with the largest growing out at an angle. In other words, Standards leave the grower looking like a little tree and Dwarf leave looking like a bush.

It is very possible that an intermediate growth/size rootstock like C-35 will be called a Standard by one grower and a Semi-Dwarf by another.

Yes you are right, my location is Australia. They are all on Flying Dragon root stocks. It's so hard to see the graft union on citrus trees unlike apple trees.

The clementine nule was sold as a standard, not a dwarf. Does it look like a graft line on the clementine?

Be careful - I think there is some confusion here.
The term 'standard' can be used in two ways. It either means it is a normal size (ie. not dwarf), or it means that it is meant to be grown with a tall trunk (and the leafy growth only at the top). The second meaning is usually for potted citrus, where a clean trunk and ball shaped growth at the top is very ornamental.
Dwarf trees planted in the open ground are preferred for ease of fruit picking. Standard sized trees will eventually be too big for many gardens and fruit will be difficult to access.
Flying Dragon is a generally dwarfing rootstock - so if all your trees are on Flying Dragon, they will be slower growing and the final size will be smaller than on other rootstocks. However, for permanently potted plants, it is the pot size that has the greatest influence on tree size.
Standard trees (meaning those with a long trunk) are not usually grown on Flying Dragon because it doesn't form a long, straight vertical stem and so the top variety has to be grafted quite low down on the rootstock. However, the top variety can still be formed into the standard shape by initially removing all low shoots.
So you have located all the graft points on your trees. This doesn't really give you any information about whether your trees are standard- sized, standard-shaped or dwarf!

Flying Dragon is a dwarf rootstock, I believe. I've got a Satsuma on Flying Dragon that's only about 5 feet tall even though it's been in the ground 15 years.