I've encountered two different interpretations of the term uke. Most common one is block. Less common but still far from uncommon is to receive.
For me personally, the latter makes much more sense. Formal 'blocks' are far too slow to be useful for anything. If a punch is inbound, you'd have to be superhuman to extend your left hand, then bring the right hand across while chambering the left, all fast enough to block the punch. I'd love to see someone demonstrate that at full speed in a free sparring setting.
Now if we consider the very same technique, but with the emphasis being on the latter interpretation, to receive, I feel it makes much more sense. Then you are receiving the offering of your opponents arm. The exact same technique applies, only this time the lefts hand intercepts and catches, pulls down to chamber, while the right arm, backed up by the full power of the hips, drives into the elbow or makes an arm bar.
I feel like the formal blocks are primarily grappling techniques. But then I'm not black belt, so I'm not qualified to make that judgement. What are folks thoughts?