It’s not as simple as 2X stronger = 2X effects. Higher THC content just means the cannabis is more potent. It takes less of it to reach the maximum plasma concentration. Theres still a “limit” to the maximum effect of the drug.
The numbers thrown around for THC content in the “old” days are also skewed. Those come from stuff confiscated by the DEA which is usually low quality, “street” weed. There was still plenty of higher THC stuff floating around, it just wasn’t being measured back then like it is now in legal marketplaces.