Oh! I didn't realize that before.
It requires 3.5 days for account value to be updated, as I thought it's instant.

Also, I didn't know that getting 100% sp of reward will give me Steem equal to SBD.

I agree with you that numbers will increase and price of SBD will be lower if difficulty not increased, but in the long run, I guess steem price will go up.

So, according to what I understood:
If Steem price go up >> SP reward will be lower amount.
If Steem price go down >> SP reward will be more amount.

and for SBD, It doesn't mater if the price go up or down, because the network already calculatr it as a stable at 1 USD all the time so the reward amount will stay as it is now.

Did I understand right ?

Thanks a lot for sharing this info with us, and I hope from you to share more info about Steem in your upcoming posts :)