This is a purpose built unit, not a restalled OEM one.
IT locks up the same, and drives the same as a stock unit. Almost no noticeable differance until you put your foot in it, then it puts you in the powerband similar to revving a manual trans to the "sweet spot" to launch.
The science behind a proper stall converter has come along way in the past 15 years.
Ask Gretchen got growl, or V6owner, PT Killa or any of the other dozens on here running them. A non lock-up would be horrible in a lock up trans.
No different stress on the trans in lock up than the stock unit.