Confirm that the Download Size column has been removed, but if you're willing and able to open the web inspector and track the AJAX requests being made to the iTunes Connect API, the API endpoint ending in `/details` still includes the data you're looking for in the JSON response, e.g.:
"sizesInBytes": {
"10.5-inch iPad Pro": {
"compressed": 8228911,
"uncompressed": 15220736
},
"10.5-inch iPad Pro Wi-Fi + Cellular": {
"compressed": 8228911,
"uncompressed": 15220736
},
"12.9-inch iPad Pro (2nd generation)": {
"compressed": 8228911,
"uncompressed": 15220736
},
`compressed` is the Download Size and `uncompressed` is the install size.
I haven't dug too deeply into iTunes Connect API access but I wouldn't be surprised if this same data were exposed.
All that said, there might be a very good reason why this column was removed, so maybe the data returned in the API is misleading.