The most important thing about definitions is that we apply them consistently. A different definition might give different answers, but it's fine as long as it does so uniformly.

> most important thing about definitions is that we apply them consistently

The most important consideration for a definition is its practical consequence.

In this case, whether the line is drawn at 1 bar or an order of magnitude more or less doesn’t materially change that, on the same measure, Jupiter was 2x larger in the past. (Less than 1% in both cases.)

In a different context, that difference may be meaningful and should thus be noted and tested for robustness.

The point is that there will be multiple definitions, so which one do you choose? From there your conclusion can be that we just use a loose definition that humans can easily grasp.