Why shinobi has hp bonus on second age?

as you see shinobi has (+15hp)
but the rest of units dont have a bonus shown on ()
how did shinobi get that hp bonus?

The only way to get shinobi before age 4 is from the consulate and all consulate units have +10% hp and attack.


why? from every civ? where is there this info?

I think probably they get the buff since the units cost export and therefore will be a little rare. The buff goes for other allies/units even artillery. As far as I know it not written in the game I found it out by playing Japan/China for a while.

Yes. All units from consulate get shadowtech as you age up.

but this is age 2 10% on age 2

all consulate units are 10% upgraded by default. yamabushi will be 10%buffed too