One reason people also do these is in a lot of jurisdictions once payment is not made ( like the jurisdiction this property is in) there is no cure period and you simply take the property back without having to foreclose. 

To say that a servicing company being used will cure the DTI for a seller that allowed their loan to be taken over has not seemed to be verified.

While this might not be the cure you're looking for, I'm sure you will find many pieces of advice from others that address your question.I'm just going to share my thoughts here because I don't think it's emphasized enough, and mostly I've had to learn this through experience:Investors are on the lookout for deals.

A lender can only avoid the 120 day rule if they are protecting their interests from a lender in foreclosure on another lien meaning, if someone is in foreclosure with one of their lienholders, the other lienholders can file right away but absent that situation, a lender must first make demand to the borrower to cure the default (subject to) and only after the borrower fails to cure, can the lender accelerate the loan (Call it due) and only after 120 days from acceleration can they file the first legal in foreclosure. so, yeah, the lender can foreclose but not in 30 days.

In the event of a buyer default as outlined in the P&SA, does the buyer get a Notice to Cure and a time period?

Without massive numbers of homes coming on to the market, we fall farther and farther behind in curing our housing deficits. 

They know you have to pay them off or they can start a foreclosure and get all of their money from you (or at auction) when you cure the foreclosure.This is a hot market and there would be other bidders at an auction. 

No pinhole leaks, cracks from expansion, or long wait times for glue to cure in freezing temperatures.

If there was an issue I would simply instruct the closing agent to insure over it if they would or cure the matter by any filings necessary.

Start with a friendly conversation and use "Cure or Quit" notices only if necessary.