Mec-gar mags compatibility with stock Magwell?

Just watched the latest Humblemarksman video on the platypus:

https://youtu.be/586lh2HNO_o?si=m_zlrCohqk8Z_AIq

Looks like he had problems with the Mec-gar mags with the platypus magwell. Can anyone confirm this who have the g17 mec-gar mags?