To be safe I'd say your conclusions are correct.
I have yet to be cut off by ST (fingers crossed!). I joined ST in Jan 2011 with a e71 sim which i put into my iPhone. It was my first smartphone w data hookup. For that first month, I didn't put it on WiFi at first and did almost everything on it (short tethering sessions included!). I must have used accumulated close to 2gb that first month!!
Then I started to read reports of ST users getting cut off from ST because of high data abuse. It was unknown at the time what that limit was so I put my iphone on WiFi whenever possible. I also looked at ways to closely monitor my data usage. I dropped my data usage to 500-700mb a monthly after my first month (i even sometimes tether around 100mb of data a month).
Later I started reading about ST having a 24hr data monitoring system. At first it was estimated to be 130mb a day (i preached and posted about this on here. Some questioning my warnings, LoL) but now it looks like it's been lowered to 70mb a day! WOW!! In the past (less then 2 months ago) there were some days when i used up 150mb within 24hrs and luckily I was not shut off or even received a phone call warning me of my data usage. Maybe it's because of my past track record on how I've used my data. Maybe this "new" daily usage applies to newer ST customers? I don't know and i highly doubt you would get a straigth answer from the company.
Either way, I'll take the "new" customer based ST guidelines into mind. As a matter of fact, my iPhone is mostly around WiFi now and I've dropped my data usage to 300mb a month! LoL.
Sorry if this didn't answer your question. But I just wanted to give my 2 cents.