The CC proponents who think it is in their purview to monitor OC activities as they feel it may affect their prima donna CC ability will now chime in and tell you fantastic stories not based in any tactical sense whatsoever, about how their method of carry is optimal.
In short: Your observations are correct, and mechanical science applies. Any extra effort or complication will slow draw time significantly. Either case is best facilitated by heightened SA, but the best technique and tooling for any scenario outside of espionage and assassination is by far, hands down, open carry.
This does not include deterrence factors also presented by an openly carrying society.
The conclusion is, and always will be, that concealed carry significantly increases the time from threat assessment to presentation due to simple mechanical movements involved.
If you can get your concealed retrieval and presentation down to 2.5 seconds, I wonder what you could get your OC down to. Just sayin...