So I am not an expert in mushroom cultivation, but I have failed to grow them on several occasions. Based on my failures, I don’t think those chunks have enough bark on them to do well as logs. So you problem may have not been freshness, but too much exposed grain, giving other fungi a chance to colonize after inoculation.
What that suggests to me is that you might have good luck chipping, and inoculating with wine cap (king stropharia) mushrooms in an outdoor bed. Wine caps are vigorous enough to do just fine on unpasteurized wood chips.
For spores: Yes, they will survive anaerobic fermentation. But then, spores survive boiling as well: thats why water bath canned green beans are a no no. So surviving spores are probably not the issue. Likewise for anaerobic fungi, which are mostly found in the gut - maybe if those logs had been rolling around in cow dung you should worry…
The main question I have would be the changes made by the anaerobic fermentation. Without oxygen, the microbes will produce all kinds of fun alcohols and acids. Since you can’t keep it sterile during inoculation, will these extra food sources encourage other microbes to settle down? Or discourage your preferred fungus? I could see this being a problem for lions mane, which is pickier, vs vigorous and versatile oysters. Or maybe that is backwards, and lions mane loves to eat anaerobic leftovers!
If you try it, please post the process and results- I am super curious!