I honestly think "chain stretch" is the term most of these mechanics use when they can't solve the timing issues usually associated with the stuck cam adjusters.
I fear a lot of unessecary timing chain jobs have been done on these vans.
I measured a brand new chains against a 152k mile chains and they were identical down to .00. If a chain with 152k on it doesn't show any notable deviation then I doubt any of these chains actually "stretch".
Wearing out the pins or between the pins could be another issue, especially if tension has been off.
All that said. It's a whole lot of work to access that chain. Best to just put new parts on while you are there. Neglecting a $100 part could cost you $3k in effort later.
I'd also just pony up and replace the "crack pipe", thermostat housing, thermostat, temp sensors, and install a trans cooler while you are in there.