On most years China wins six golds, so more slots would definitely lead to more golds.

of course they are. The Chinese team selection tests are notoriously more difficult than the IMO, and they enforce a one-time participation limit. If they were to send 24 people, not only would they probably be returning with ~20 golds, they'd be taking away the golds of the other nations (as only the top 1/12 get gold)

Yes, China having more slots would mean unclear factor of more gold medals for China. (Although China has only earned 6 gold medals in half of its years, and 5 or 6 gold medals in only 24/34 years, despite having 1/6 the world population so proportionally should claim ">8" of the ~50 gold medals each year, so China does appear to be under performing the average country (per capita) in half the years.)

But those 4 smaller countries having 1/7 slots wouldn't mean 1/7 gold medals, since they only send 5-10 gold medalists each year in those slots.

Romania averages over 1 gold medal per year. China, with 70x the population of Romania, should easily be getting 6 gold medals per year almost every year and about 70 theoretical golds of their deep bench got tested, if it has comparable per capita performance to Romania.

Of course all these stats are kind of silly because of sampling limitations.