Yeah, regular users of opioids can take high doses that would kill someone who takes the same dose without built-up tolerance. Junkies who OD or fentanyl usually have a high tolerance, which skews statistics.

Be it under prescription for moderate and high pain, or recreational users / jukies chasing euphoria, that tolerance quickly lowers if you stop taking them.

Which is why junkies who go clean for a while can accidentally kill themselves by taking their former shitfacing dose.