Windows 7 August 2018 Ultimate (x86 and x64/en-US)
both point to same link x86 version, there is no download for x64 version.
Also why not proving security monthly rollup downloads as well?
for example: http://www.catalog.update.microsoft.com/Search.aspx?q=KB4489878
2019-03 Security Monthly Quality Rollup for Windows 7 for x64-based Systems (KB4489878)
The full list of monthly rollups KB's could be obtained from
https://support.microsoft.com/en-us/help/4009469