Step-up in basis - a reason for separate accounts in marriage?

I recently learned about the step up in cost basis a child receives when inheriting a brokerage account from a deceased parent. Their cost basis is now the fair market value on the date of the owner's death, which of course could result in huge, un-taxed gains since the original purchase many years ago. From my reading, a spouse is entitled to the same step up in basis *only if the brokerage account was solely owned by the deceased spouse - NOT if it was a jointly owned account.* I just so happe