Not true at all and not sure why people keep saying this. Kratom is literally a slew of alkaloids not just Mitra and 70H-mitra. Which means those variegated preparations have different effects. The variation in effect from the literally 100s of different kratom strains and brands I've tried vary widely. Even full spectrum extracts will capture these other alkaloids which gives you an effect that represents the totality of the plant. To say it just contains Mitra by itself goes against basic science and knowledge of this plant. It's like saying cannabis is just THC and nothing else which we clearly know is not true.
They prepare the kratom in different ways which is where the strain nomenclature comes from. Please stop discrediting science and human experience by saying strains are all the same, go buy a red, white and green strain and try them yourself you should notice a difference. Some people who aren't experienced with drugs or inebriating substances don't have the foundation to describe the difference which I understand completely my brother is like this but plenty of us who are in tune with how substances affect our bodies can write all day long about the variations.
Read this from a research publication:
Kratom produces more than 40 structurally related alkaloids, but most studies have focused on just two of these, mitragynine and 7-hydroxymitragynine. Here, we profiled 53 commercial kratom products using untargeted LC–MS metabolomics, revealing two distinct chemotypes that contain different levels of the alkaloid speciofoline. Both chemotypes were confirmed with DNA barcoding to be M. speciosa.To evaluate the biological relevance of variable speciofoline levels in kratom, we compared the opioid receptor binding activity of speciofoline, mitragynine, and 7-hydroxymitragynine. Mitragynine and 7-hydroxymitragynine function as partial agonists of the human µ-opioid receptor, while speciofoline does not exhibit measurable binding affinity at the µ-, δ- or ƙ-opioid receptors. Importantly, mitragynine and 7-hydroxymitragynine demonstrate functional selectivity for G-protein signaling, with no measurable recruitment of β-arrestin. Overall, the study demonstrates the unique binding and functional profiles of the kratom alkaloids, suggesting potential utility for managing pain, but further studies are needed to follow up on these in vitro findings.