I disagree that the last-minute timing is not an issue…its...

I disagree that the last-minute timing is not an issue…its last-minute relative to the option expiry but in doing so has overlapped with an active drilling program.
Exercise of options is generally a risk…unless it’s an off-market conversion/sale, or unless the stock is sold immediately. So, any additional information that insiders are exposed to during market sensitive programs has the capacity to change the risk profile…hence good practice (imo) would be that any such share movements or option conversions are made ‘outside’ that window. That way, any such concerns re unfair advantage cannot be bought into question, full stop.

By way of a hypothetical example:
If person-A, who IS NOT privy to the daily workings has X-options in the money that are imminently about to expire…then they have three main options (pun intended) 1) let them lapse (would be silly). 2) convert them and sell straight away, take the profit. Or, 2) if they think the sp is on the way up, then they convert them and hold…taking the risk into consideration and using the information that the company supplied to the market to guide them.

If person-B, who IS privy to the daily workings has X-options in the money that are imminently about to expire…but because of their position they cannot sell the shares straight away, well then that leaves them with two choices. 1) let them lapse, or 2) convert them and holds the shares for a later time to trade…taking the risk into account.
Now that’s all fine…except if Person-B makes that decision at a point in time when they have access to information that changes the risk profile i.e. drilling details/visuals etc. Because in such a scenario it would leave person-B and the company open to question and/or speculation on unfair advantage re was that decision (to convert options to shares) influenced by un-released market sensitive information.
Imagine a scenario where directors convert options during a drilling program, make a discovery and the sp rockets…people would be well within their rights to question the timing around that. Even if it was a coincidence, there is potential for unnecessary reputational damage.

Now in this instance for DRE, if this drilling does result in a significant discovery...well I'm pretty sure no one is going to care about the timing of a few converted oppies...which is fair enough. So, yeah nothing untoward...other than (imo) sloppy timing from management who I generally hold in high regard, which is why it surprised me that it didn't happen pre the start of the drilling.