After disabling "No more hidden variables" and starting a new game the gold the Natives own is no longer shown in the Score list.
Exactly, when
"No more hidden variables" is disabled you will
not always know how much gold other Nations have.
(You basically see the same in the
score list, as you do in
Vanilla.)
So this is
no bug.
This is
"No more hidden variables" just "working as designed".
(If you are really trading with them, you will still get some information about gold - you just do not see it all the time.)
They are still shown when I try to buy their goods - ...
Hm, never noticed that.

But it is ok for me, because you entered a real trade negotiation.
So it is also
no bug.
(
We can not change it anyways, because the Trade Sreen is in the exe.)
Then the 9000 gold at the top left vanish and only their offer of around 4000 gold is shown.
Yes, there is a
setting and according logic for
max gold a Native Nation will be willing to trade with you in a
single trade transaction.
(It is supposed to
prevent exploits and also to
prevent stupd AI behaviour when trading with natives.)
Once you make your first offer, the "max. gold per trade transaction" will be checked.
(And listed in the trade assest list like that.)
This is also
Vanilla behaviour by the way.
This setting is however
only considered in
"normal Trading".
My
"Bargainig" feature
is able to work around / ignore it.
So again, it is also no bug.
(And again,
we can not change it generally - we could only the setting "max. gold per trade transaction" but we would potentially allow exploits / stupid AI behaviour in
normal Trading.)
----------
Seriously guys,
not everything is a bug.

(Bugs are mainly things that are broken and not "working as desgined".)
Sometimes there are reasons for things working as they do.
Those reasons might often simply be
"technical limitations" or to avoid
"incredible efforts for implementation".
But in other cases the feature was really
designed to work that way.
But of course I know, that it is difficult or sometimes impossible to understand them all if you are not a modder.

Sometimes we simply need to understand though, that this is
just an "imperfect game" that needs to make compromises and not always as realistic, consistent or correct as real world.