Who said anything about infinite Bitcoin growth? Its still in its early innings and has a long growth run way ahead of it before it matures.
Investing in Bitcoin today is like investing in tech stocks 20 years ago. Bitcoin will eventually mature and become low growth but that is still 10+ years away.
And I own both Bitcoin and physical precious metals but for what its worth my Bitcoin allocation is 10 - 15 times my precious metals allocation. You want to own some physical precious metals as a hedge against the internet/electricity being disrupted but in terms of returns BTC is going to smoke precious metals over the next 10 years so allocate accordingly.