It seems to be based on injury rate data submitted to OSHA in three categories ("Lost Time", "Light Duty", "Other"). That's fairly simplistic, so I'm not seeing where the union had opportunities to present the data in an unfair way. The comparison to WalMart, for example, seems straightforward.
I do agree that some of the charts based on surveying workers might be biased, but that's the least interesting numbers in the report.
The BBC used the term "study" as if to imply that, but the SOC did not. It's a standard analysis or report, like you'd find in a trade or policy publication.
"Our findings are based on data that Amazon and other employers provided to OSHA annually from 2017 to 2020 within the General Warehouse and Storage industry (NAICS: 493110) and the last mile delivery industries (NAICS 492110 & 492210). ... All employers are legally required to submit annual injury and illness reports to OSHA for any warehouse, delivery, grocery, or wholesale trade facility with 20 or more employees annually, so these records should include every significantly-sized facility in Amazon’s US logistics network."
That's shoving a square peg into a round hole. Amazon's competitors have the same labor pool for their warehouses, so it can hardly explain an 80% difference in injuries.
If Amazon and Walmart warehouse workers want to form a joint union there is absolutely nothing stopping them and it'd probably be a pretty good move for worker's rights. But, while Amazon is clearly anti-union, Walmart hates them vehemently.
This pattern of comment includes accusing someone of “being bias” (instead of “biased”) and implies that noticing bias is somehow a debate winning move.
Bias is a thing, having bias means you are biased towards one position or away from another. You should be biased in many ways - e.g. preferring human survival to human extinction would be a reasonable bias. Preferring the word of your friend to the word of a stranger, another.