Netflix is logging your whole activity. Meaning IP-address / device and the time of course. I don't know the exact data which Netflix is aquiring from your device, but it's not difficult to get your hardware ID you are using when logging in with your mobile device. So, while your IP-address is changing, your hardware ID stays the same. Thus, they are aware of you being the user of that mobile device.
My IP-address changes each 24 hours, or when I reconnect to my provider. But try to explain two or more Smart TV's which are actually stationary with each having a different IP-address streaming Netflix at the same time. All that stuff is being logged. You can also verify this on your own for the last 60 days.
This post should have ended at the bolded.
You are talking absolute tin foil hat levels of "well you could do X and Y so maybe they are doing it" Like I said, the post and your whole thoughts in this thread are based on a small amount of networking/PC hardware knowledge and the sort of paranoia you find in a VPN commercial.
As for the OP and Netflix sharing, aye, I've got a 4 screen 4k account and 4 different places are logged in with that, had it for about 2 years with the current group of people and really it's no issue, but of course if you have basic netflix account you can just have it on a single screen, you need the higher tiers to allow multiple viewers at once.
As for doing it because of how much Tax they pay.... what does that have to do with me? You think Netflix is the only one that makes use of those loopholes where billions are funneled through? for a laugh you should see how Apple used Ireland's tax loophole to funnel every sale in Europe through their branch in Cork to pay effectively no Tax on it (I think somewhere in the region of 50cent per million euro) I'm not saying Netflix doesn't use loopholes to avoid paying it, but there are bigger fish in the sea avoid paying it and being honest, I'd rather my €15 a month goes to creating new content and shows for me to watch rather than Netflix CEO having a conscious and using that money to fill in a giant hole left by Apple and Co.
This is worth a read, it's good stuff https://fora.ie/apple-eu-ireland-state-aid-2955114-Aug2016/
"the commission said the deal between Apple and Ireland allowed the company to pay a tax rate of only 1% on its European profits in 2003, with that figure sliding to as little as 0.005% by 2014."
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8