They're doing the same upgrade & expansion & not a rebuild. As I understood it a complete rebuild meant the stand was closed for 2 seasons.
I suspect the key things from the clubs perspective is a significant development cost saving by completing the stand expansion in one year rather than two. The loss in revenues from tickets will be offset by probable Champions League money & I'm sure the PL & UEFA would make allowance for rebuilding. The income from the upgrade will be available a year earlier, well in advance of the Euros.
I'm sure the club have done their sums & that this is the best financial decision, if not the best for supporters in the short term.