MEC function and its integration with WooCommerce is as follow:
In MEC, payment is set on Woo, when the user who is booking clicks on checkout, the payment data are sent to WooCommerce.
If the payment is done completely and successfully, it returns "true" answer but if not, it will return "false" and the payment won't be done.
Despite the WooCoomerce process in payment, when the payment is done and is returned to MEC as true, the booking is done successfully.
MEC emails are sent and a new record as will be stored in database as a new booking.
The functions in WooCommerce and MEC are totally different and are not related to each other. The successful or unsuccessful status of the payment is sent from Woo to MEC only. This was the whole process of integration.
Please refer to WooCommerce documentation and support and if you require more explanation and details of WooCommerce functions, you can ask them.
Please Note: The event has not added to cart, In other words, an event is not a product.
Update: Now "Add To Cart" is available: https://webnus.net/modern-events-calendar/addons/
Documentation Addon: https://webnus.net/dox/modern-events-calendar/woocommerce-addon/