Hey @jdoe123 - welcome to the US Huel forum!!
The factors that played into the switch are complex and while we cannot disclose more than that, we can assure you that testing is still done to ISO standards! 
Well done Robat and team. I checked your numbers they square up nicely all within the ballpark regardless of the approach. Good job in recognizing the impact of ratios on final doses. The impact of lead in adults is one of the better understood heavy metals given we have such a long history. Much of it is encased in long bone and presents very little issue again in adults, we just see it in the ZPP urine tests but there’s no appreciable systemic deficit. Furthermore. the amount of lead absorbed through the gut tends to be rather small particularly if the person is well fed (had a meal at least 6 hours prior)>
For further reading on the toxicological profile of Lead and other heavy metals, consult the CDC’s ATSDR toxicological profiles, available online and updated routinely with new research findings.