Question about Python-Steem: real curation rewards ?

I'm playing with the latest Python-Steem release.
I made this little script, that adds up all my curation rewards, ever.

I'm using the Account.history function to list the rewards.
When I add them all up, the number doesn't match the curation_rewards as shown by Account.export.

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Code

from steem import Steem
steem = Steem(node="wss://node.steem.ws") #issues with this.piston.rocks atm
from steem.account import Account
from steem.amount import Amount

account = Account("felixxx")

reward_sum = 0

for event in account.history(filter_by='curation_reward'): 
    reward = Amount(event['reward']).amount
    link = event['comment_permlink']
    #print(account.converter.vests_to_sp(reward), ' SP for ', link)
    reward_sum += reward

print('reward (in vest): ', reward_sum)
reward_sum = account.converter.vests_to_sp(reward_sum)
print('reward (in sp): ', reward_sum)

curation = (account.export()['curation_rewards']/1000)
print('curation according to Account.export (in sp): ', curation)

Result

Shouldn't those numbers be identical ?