The FS_CHMOD_FILE and FS_CHMOD_DIR constants are specifically used by the WP_Filesystem classes, and may not always compare directly to what the files should be set to when written directly to disk (as they're designed with the FTP subsystem in mind, something the Uploads do not utilise at all) - As a result, using these same constants for file uploads could cause more harm than good.
For example, Files are set to 644 by default, this would be correct when uploaded via FTP (as WP_Filesystem) will be doing, however, when written to disk by apache running in an insecure mode (u/g apache/apache for example) requires the folder to be 777, and as a result, files as 666). I'm not saying it's not wrong to have a secure server, simply showing why re-using of those constants is not in the best interest.
0710 directories
It seems to me, that setting this to 0750 would result in WordPress uploads working correctly (purely as a point of reference for a working configuration), and is the scenario that one would expect to find the directories configured for (Apache can Read the folder list, as well as change into the directory).
for the less informed on the results of a 710:
7 - Owner - Read/Write/List folder contents/change into
1 - Groups - Change into (But not list files)
0 - Everyone - No access
Setting directories to 710 seems overkill to me, although, one which can be seen as a "highly secure" (in other words, highly limiting) permission level, I would argue that it should be Apache who should be configured to not allow directory listings in this case.
Also, for what it's worth: I'm sure there are filters in the upload process which can be used to change the permissions of the created files, although, I don't know them off the top of my head (I'd check CDN plugins if you can't spot it in the code)
