Lansweeper scans anti-virus programs both out of WMI where available (which includes status information), and by comparing software installations with the anti-virus lists, the latter is customizable, but the former is not, and is pulled directly from the local computer. More information on the anti-virus scanning procedure can be found
here.
As long as Windows Defender is found when querying the anti-virus WMI class (Securitycenter/Securitycenter2), its existence and status will be listed on individual asset pages.