You think Red Sox "needed" Eovaldi? For what?
I am going on the premise that you did NOT think Yanks needed Britton (easy, since this is basically what you posted)
The 2 deals are identical, right down to the "we kept him from the opposition" stance.
The deals were not identical.
Britton was an established star closer, Eovaldi more of a lottery ticket starter.
Sox got priced out of the reliever market but could pick-up an end of the rotation starter who might be moved to the pen, or allow someone (Pom) to be moved to the pen.
Britton had a deep market
No one else wanted Eovaldi, which is why the Sox could get him.
and fwiw when I put forth the Ys keeping Britton away from Sox/Astro's was a tangible benefit, a return response disagreed with me.