Can switching ADHD medications change someone's weight trend even at an equivalent dose?

Yes, this is something people commonly report. "equivalent dose" conversions between different stimulant medications are approximate rather than exact in terms of individual effect, and different medications can have somewhat different appetite-suppression intensity for the same person even at a clinically comparable dose. It's one of the practical reasons a medication switch sometimes comes with noticeable appetite or weight changes that surprise people expecting a seamless transition. References: https://obesitycanada.ca/healthcare-professionals/adult-clinical-practice-guideline/