If other browsers are also included by default, it is not antitrust to include that browser by default too. The only reason the share of Chrome would be interesting for antitrust would be if that share were leveraged to promote a product in another market, which nobody is claiming.
Actually that's exactly what the claim is: That Chrome being mandatorily included and set as default is used to promote Google Search unfairly. That's directly in the EU's statement.
No, the claim is that they're using Android's dominant position to push Google search and other Google products. Chrome's default in itself is not an issue.
