So let's take a look at these links.

From the first one:

We also find substantial variation in management practices across organizations in every country and every sector, mirroring the heterogeneity in the spread of performance in these sectors. One factor linked to this variation is ownership. Government, family, and founder owned firms are usually poorly managed, while multinational, dispersed shareholder and private-equity owned firms are typically well managed.

I don't think this supports the claim made.

The second link points to a NBER article behind a paywall (for me). Looking at the abstract, however, it doesn't say anything about preferences for long-term vs short-term. The most relevant data point that I see is that private firms invest more (as % of assets) than public firms, but I'd want to see the details of the study before coming to a conclusion about what that means.