There is a continuous disclosure rule for ASX companies, so that...

There is a continuous disclosure rule for ASX companies, so that information that would have a material effect on the companies SP has to be released when the company knows about it.

Of course there is a little bit of wriggle room in there, for a company to hold onto results that they don't think would 'materially' effect the SP.

IMHO it's getting more likely that some of the results were above grade and needed to be re-assayed by the lab, which of course takes longer to do. So it's very possible that the extra time being taken is a positive sign for some of the expected results.
ENR themselves might only be getting all the 'batch' results at the one time from the lab, so if some were higher grade and needed re-assaying, it's holding up the entire 'batch', hence the longer time frame (we can all hope anyway).

Right now we are 5 weeks since the last announcement, which is about as long between any price sensitive announcements over the last year, except for 6 weeks over Xmas...