If I'm reading that right, that could also say that Instagram is suppressing anti-israel content? It's just saying that in comparison to Instagram tiktok is showing more x, y, z. But Instagram is absolutely not a neutral point to measure from.
For starters there's different demographics on each one, but I'm sure you could adjust for that, maybe the study did. But I don't think you can adjust for the impact the US government has on Meta. I don't believe for an instant that some US agency isn't manipulating algorithms or requiring certain tweaks to steer discourse just like they did with US news outlets.