OT - Using sous vide for canning

How much headspace was in the jar?  And was the lid too tight prior to processing?  In order to create a vacuum, you need sufficient room so when the headspace (air) cools and collapses it sucks the lid down.  Properly sealed jars with a collapsed headspace vacuum barely even need the screw ring.

Part of canning is killing bacteria that could spoil the product so, for canning and the vacuum to form, you should really get it to somewhere north of 200 - say 211 boiling point for 15-20 minutes. 

As they say, use the proper tool for the job. 

I tried that recipe once.  I didn't think the pickles were anything special, and IIRC only one of the jars sealed on cooling.  I kept them all in the fridge, then got rid of them a month later when they were uneaten.

To @nolaegghead 's point, 250F is fairly standard for commercial sterility/retort processing of low acid canned foods (LACF).  Lethality of clostridium botulinum (the bacteria used as the basis of LACF thermal processing) begins ~220F, but is very slow to accumulate at that temp, so we generally process at temps 240F+.  

For what you are doing; acidified food processing (pH<4.6): vinegar=acid=more growth inhibition=lower processing temps.  Adding acidity essentially narrows the range of bacteria to be concerned about to microbes that are much easier to kill with heat.  Measurable lethality in acidified foods begins at ~170F.

The real target is to have your product above specific a temp (the temp at which target bacteria begin to die) for a specific time duration.  Once at or above this temp, you begin to accumulate lethality.  The higher above, the more rapid lethality occurs.  So if you preheat you product, it will technically achieve this processing temp quicker, but tbh, in a small batch, it's probably negligible.

/nerd rant over