You can not change the growth rate for investment plans above 1%.
Upon selecting any growth rate other than 100 % at the payout screen sets the system automatically it to 100 %.
It means you wont see any cents until your plan ends.
Bitcoin.com is just one domain name used to promote Bitcoin. Bitcoin.com is not an official website. Just like nobody owns the email technology, nobody owns the Bitcoin network.
As such, nobody can speak with authority in the name of Bitcoin.