Waiting for a highest and best call makes sense when a seller has firm signals that other serious offers are close behind, since Saskatchewan REALTORS Association data shows tight-supply months producing more of that competition. Accepting immediately makes sense when the first offer already meets the seller's price and terms and the risk of losing it outweighs the upside of waiting.
A seller who waits and calls for highest and best risks the first buyer walking away entirely, since that buyer has no obligation to resubmit once asked to compete, so the tactic is not free even when it works.
The right call depends on how strong the first offer actually is against real comparable sales, not on a rule that says to always wait. Get your hand-reviewed valuation from Joel Dyck.