Profitability is directly related to turnover. PSR being profitability and sustainability rules, is also related to turnover.
Interest or financing costs (external or shareholder loans) are usually a small amount in a P&L even if a business is highly geared. In your example of arsenal saving £25m a year, whilst it is a large amount in its own right, relative to turnover and some of the other costs such as players wages or amortisation, it is a small cost. So there is benefit in using shareholder loans (or was up until now) but if tested for arms length principle, it won't be a significant benefit going forward.