That much speed differential over a period of 120 seconds requires an average acceleration of about 51,000 G. It is possible for specially constructed electronics to survive G forces in that region.
That speed would make the flyby portion come and go in seconds. There would be measurable relativistic time dilation, but it would not be a deal-breaker.
It isn’t so much the electronics - well, yes, that too - but the fact that they’re talking about hanging this thing off a sail that leads me to wonder what is going to be able to withstand that. Well, in any case the article is specific about the projecting requiring major advances in technology. I’m guessing this is one.