That information only applies to mobi files you plan to publish to Amazon with DRM. For personal use or publishing without DRM Calibre is fine.
Aside from that I haven't seen a discussion in the Calibre forums that confirms that allegation - note I'm not saying I disbelieve the info, just not sure of the technical details around it.
If you do need to publish to Amazon with DRM then check out this post for a workflow which should let you get the best of both worlds:
https://www.mobileread.com/forums/sho...56&postcount=7