This is just plain incorrect. Every cryptocurrency's rules can be changed via hard fork. Bitcoin doesn't have any magic property that guarantees there won't be a hard fork affecting the emission schedule.
Bitcoin is hard to change the similar way TCP/IP protocol stack is hard to change.
[0] https://news.bitcoin.com/5-mining-50-btc-hashrate/ (I fully understand this is a pro-BCH site but their sources are accurate)