No, this is not a typo, Sony is in fact offering 250 games of the classic PSP library, for free in Japan.
If you reside in Japan, have a PS Plus subscription, and a PS Vita, Sony is offering 250 PSP games for you to download on your handheld, free of charge. Sony announced the news this morning during its briefing, and never mentioned anything about a similar offer to the western audience.
The offer runs from September 17 until the end of the year, and as with any PS Plus offer, you keep the games you download as long as you have an active subscription to the service. Do bear in mind that some PSP games will still be available at a cost, but a large number of them will be available for free.
The list of all available PSP games is 374 games strong, and Sony did not yet publish a list which of those are included in that offer.