They absolutely did not.
During the PTR where extra Stash Tabs were introduced there was a stickied thread on the PTR forums asking specifically for people to report any issues with the Stash / game. Not a single report was made. Not one.
During that PTR which, if you recall, initially offered 5 extra tabs, bought for gold, it took us up to 17 Stash Tabs. I bought those within the first few seconds my heroes were on the PTR and played it for the entire time the PTR was up. I played solo and in groups and didn’t have a single issue with it.
Many people did exactly that, and none of them reported an issue. Blizzard’s response was that the problems might start to occur if all 17 of the tabs were completely filled, with single square items, especially if lots of them were rings / amulets with gems socketed into them (as presumably that counts as a double item).
First they said it would cause client problems / crashes. Then they said it would cause server problems / crashes. Then they came out with the stash synchronisation explanation. Eventually, having gone through a number of reasons / excuses, we ended up getting one extra tab, obtained by Conqueror.
It made the report I submitted the following PTR even funnier…