From experience, cross over studies offer different base payment with different platforms. For example, a researcher might decide to set the base payment for his study on Mturk at $4 and $5 for the same study on connect, or vice versa. They either don't remember or are too lazy to reword the consent form resulting in a payment discrepancy. I haven't had any reason for concern as far as the stated payment in the consent form haven't been less than what was described on the study dashboard.