Nope, this is definitely not true. No "wall" at lvl 70, the correct number is 85-95 (it's somewhat subjective what one considers "hitting a wall" so I can't give one specific number but rather an interval).
The progress slows down as you get to higher levels (because it's based on a logarithmic scale). What we have here is effectively a "soft cap".
"Hard cap" is when you go at full speed and at certain point suddenly can't go any further.
"Soft cap" is the same but with a gradual slowdown before you hit the wall.
The end result is the same, there is a limit. I suspect in EU this limit (aka "soft cap") is somewhere around 95-100 but there's no meaningful progress a few levels short of the ultimate limit
(unless MA has changed the system in last 12 months or so).
Around lvl 70 the progress is getting noticeably slower but it's not the same as no progress at all. I skilled past lvl 85 AGI naturally. It took me years but if I was able to do that, anyone can.
I fully agree with your second statement. If your goal is to get high attributes it's a good idea to keep the tokens until you hit the soft cap. Most people give it up a few levels too early and end up regretting it later. That's just human nature. We're impatient suckers and there's nothing we can do about that.