adnd 2nd – A priest from Erik receives ALL the powers of a druid?

In the Birthright Rule Book, on page 74, it says the following about Erik's priesthood:

PW as a druid, no longer move silently, hide in the shadows and empathy of the animals
as a guard three levels higher

Since Birthright, there is more than one church of Erik and the leader of the religion is a regent who can be a npc of level 1 (or a player) and at the 15th level (of PH):

The Great Druid knows six spells of each level (instead of the normal game)
spell progression) and can also cast up to six additional spells
levels, either in one spell or in multiple spells whose levels
total to six (for example, a 6th level spell, six 1st level spelled,
three 2nd level spells, etc.)

Or it is not considered a druid, since it comes from the position, because its servants also receive:

Three of these nine are archdruids who roam the world, acting as his
messengers and agents. Each of them receives four additional spells
levels.

If so, the powers of hierophants are also ignored? Since their origin stems from the status of hierophant and results in a cost of spells:

Beyond the 15th level, a druid never gains new spells (ignores the
Priest spell progression table from this point). Casting level
continues to increase with the experience. Rather than spells, a spell
the powers are acquired.

P.S .: I was not able to create a Birthright tag for reputation reasons (Birthright is a campaign parameter for Ad & d 2e)