I think "modified human" is one class of things that counts as a construct. (Whether there are minor modifications that don't count for wasping purposes ...?) Adam and Lilith count as constructs, and I think Klaus does, too.

Wild speculation: the spark wasp was tuned for sparks, not construct-sparks, so its hold on Klaus is not as strong as it would be on an unaltered spark. (That he's far better than average at bending orders is likely, too.)