You expect to be able to use pu in place of cu in front of a selbri to close the front sumti - right? Wrong - if it's an abstraction!
lenu mi klama pu vajni is a sumti with parse:
({le < [ [[nu (mi {klama < [[ [[pu KU] VAU>}) KEI] vajni> KU} VAU)
I don't. Sounds like someone mislearned that tenses mark the start of selbri.
To be fair, the book says (10.1, p. 216) The placement of a tense construct within a Lojban bridi is easy: right before the selbri. It goes immediately after the "cu", and can in fact always replace the "cu". Of course, it then goes on to say (although in very complex sentences the rules for eliding terminators may be changed as a result).