The solution you mention does the work because in version 1.5.0 we added an upgrade script that moves all the data from post_meta to the new atum_product_data table. So each time the version number in db changes, it runs the upgrade automatically.
But doing this could be dangerous, so use it with care.
You can still use the 126.96.36.199 version but this version is deprecated and won't be updated anymore, so you won't have all the fixes or improvements that we add in future versions. Also, this old version, won't be compatible when WooCommerce launches its new tables structure this year: https://woocommerce.wordpress.com/2018/07/17/woocommerce-custom-product-tables-beta/
So we don't recommend you to do it this way. This is only recommended when the upgrade to 1.5 failed for some reason and the atum_product_data table was not created or populated.
FYI, we are currently developing our own add-on for exporting/importing ATUM data. So when available, you'll be able to do this and much more in an easy and secure way.
Until then, you could implement your own solution to move the data from post_meta to atum_product_data. If you are a developer, you can go to the ATUM's Upgrade class and take a look at the migrate_atum_products_data method. If you don't know how to do it, you can find a developer to do that for you and to run that code (with some modifications to updating instead of inserting if needed) when you import the new data.
Hope this helps.