When registering a Google Ads account, matelso asks for the rights of an administrative account in your Google Ads account. Here matelso does not ask for ownership rights.
In an infomail to its customers in June 2020, Google describes the step that only exactly one (1) administrative account can have owner rights. This right is not queried and is not required for a functioning integration of Google Ads in matelso.
You should therefore see a “No” in the Owner column in the “matelso Call Tracking AdWordManager” line in your management account view.

Management accounts can only be managed by one (1) management account. This means that the matelso Ads integration cannot transfer data to a managed management account. This restriction does not apply to Ads accounts themselves, only to management accounts.

An Ads management account structure can be a maximum of 5 levels deep. Once these 5 levels are reached, no managed account can be switched through the structure and Ads integration must be linked directly to Ads accounts.