@bcohen
Its possible that an additional valid bid could be found after 1:30 but using this as an internal cutoff helps remove uncertainty from the auction.
Sorry you missed the bidding, a countdown timer will definitely remove the uncertainty regarding the time zone factor (I too felt unsure for some reason).
While randomness of block confirm times definitely adds a twist to bidding, no bidders are advantaged by it, as all share in the risk of later bids not counting. Maybe it makes bidders lay their cards on the table sooner? Maybe it encourages speculative Hail Mary bids that may or may not make it into a block before the auction end time? It's definitely different than the straight-forward eBay-style bidding you were championing for, but I see this particular quirk as more of a fun twist to standard bidding, than an issues that needs solving. For me, the quirks kind of add to the richness of this experiment we're all participating in.