Bought her a "granny mobile" and have it at local mechanic to do some routine maintenance.

They want to do a coolant flush and replace the orange dexcool coolant car has been in it now with universal coolant. He said GM Dexcool used to be different in the early 2000s, propylene glycol base, but now everything is ethylene glycol based and now all of the new car manufacturers will have there "brand" with a different dye color but is all the same stuff......true or false?

False.

Unless approved by the manufacturers. Don't mix disparate coolants unless you want a gel nightmare.

Yeah mixing Dexcool with other types of coolant was a no-go. Concern would be if some Dexcool is trapped in the block and mixes with the new non-compatible coolant and causes a problem.

Thanks, that is what I thought, I know prior owner had serviced exclusively at dealer and had serviced with Dexcool only. Shop tried to say they would flush it all out, but if even is left in there would be a mess. I told him to just stick with the Dexcool

Careful letting them proceed with the flush. His flush equipment probably has the non-dexcool stuff in it. And he may not be willing to change out what is in his maxhine. If you trust this shop to really do as you asked because you have a prior relationship that is one thing. If this is your first time using them I would probably just tell them to skip the coolant service. Best case, they charge you for a large quantity of dexcool to do the job with their machine, most likely case they just do a drain and fill with dexcool and charge you for a flush. Worst case they mix coolants because they think they know best.