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True. Although fringe interests can sort of get representation in a two party system, they just have to do it through one of the major parties. Which is admittedly a much harder deal for them that gives them less negotiating power than if they were an actual party with their own leadership.
Both systems involve the formation of a coalition of different groups; a two party system just forms the coalition before the election, and a multi-party system forms the coalition after the election.
The 50/50 split is not a matter of statistics but of sociology, and is a feature of two-party systems. In such a system, it is a bad idea to focus on issues that have support from only a tiny minority, because the opponent will pounce and easily capitalize and take the much more popular position. So in a two-party system, political discourse is often dominated by wedge issues over which the populace is divided roughly 50/50. You can see this in other two-party systems as well, such as Brexit in the UK during the previous general election. Wedge issues shift over time: the Republicans in the US have moved away from homophobia as the acceptance of homosexuals has steadily increased, and shifted towards transphobia.
The dynamics is very different in multi-party systems. In such a system, it can be beneficial to focus on minority issues and interests, if there is a small group with strongly held beliefs. For example, in the Dutch national parliament there is a party that supports a literalist interpretation of the Bible, including support of the death penalty (which is banned in the EU), even though only 10-20% of the population regularly attends religious service. There is also a party focusing on animal rights, and an openly anti-Semitic anti-immigrant party. In a two-party system, such fringe movements would not survive.