In reply to MIROSLAV GLAVIĆ.

It should be noted most of the developers here don't take on client work, but instead are plugin or theme authors. I don't get paid for support unless you buy premium support. In which case you still have a ton of people to manage. Skype/Hangouts is a horrible way of doing things. If you have 300,0000 clients, and 1% pay for premium support, that's 3000 users. If I did every fix via hangouts or skype for every one of those users I would never have time to eat.

Like the original WPBeginner post said, its fine if you don't want to give main site access, but the staging site needs to replicate the same behavior.

Necessarily speaking, walking a client through debugging is a horrible waste of time. You have to get the clients to install browser extensions for certain situations, plus then you have to waste the client's time doing the debugging. If they've hired me, or they're using my plugin, they shouldn't have an issue with me back there. Theoretically, like I said earlier, the difference between you giving me backend access and me pushing an update of my plugin that gives me that is nothing. While I'd never do the latter, there are some nefarious people out there that would. If you trust my plugin or theme on your site, you've invested trust in me.

Reputation might be baised but only you influence your trust in me as a plugin author. If you install my plugin, you trust me. If you install Piet's plugin, you trust him. If you don't, then you shouldn't be installing our plugins.

There's also alot of good reasons for needing full admin (subsite or non subsite). For example, if you have a site where you have a plugin that adds fields to the edit user tab that only admins are supposed to have access to, and thus would be protected by a capability check to edit_users, there's no other alternative to debugging that. Sure, technically you could make a custom subscriber role with that capability, but most role and capability plugins out there either don't work, or would take 50x as long for the client to add that role as it would take for me to solve the initial problem to begin with.