Unexpected Laguna Sites Included in design.getSiteInsts()

[RipperJ]

Hi. When I'm using design.getSiteInsts() and filter the laguna sites (SiteTypeEnum.LAGUNA) in it, I found some sites whose inner laguna registers are not used but included in getSiteInsts(). For example, as the following figure shows:

This site is included in getSiteInsts(), but whose property "IS_USED" in Vivado shows false.
Is this expected? If so, is it because that the wire connecting RXD4 is used?

[clavin-xlnx]

Generally, those SiteInst objects should probably not be included. Can you provide more information on how this design was created? Are you able to share an example flow that causes these to appear? We would be interested in tracking down the cause for their existence, thanks!