Dunno why everyone in here is speculating when the heart of the issue has been right there since the review kicked off: https://www.reuters.com/business/elliott-offers-1-bln-help-separate-western-digitals-flash-business-2022-05-03/

The spinoff is as simple as the current valuation of the two companies together doesn’t make sense. Bank analysts are suggesting the HDD business on its own nearly constitutes the entirety of WDC’s current market valuation. Which means the flash business unit would intrinsically be valued at $0. Which is idiotic, and Elliott knows that. Force the spin off, and WDC will remain close to its current valuation, and the $0 flash BU valuation will immediately be “re-valued” at something significantly more than $0, thus making money for all the shareholders, particularly those with more than 6% ownership in the business.

WDC’s flash is manufactured through a joint venture. Flash-related IP isn’t really at risk of being retained by WDC since it is owned by the JV itself…