update statistics not recommended!

My new site has a third-party financial package (Lawsons), running on v7.13. The underlying DBMS is Informix. The Lawsons help desk has told me that they recommend that we never run UPDATE STATISTICS, as it will degrade performance. Their reasoning, allegedly based on empirical evidence of their users, is that all their SQL is written with where clauses, and the indexes that exist will be used, which is what is required. If we run an UPDATE STATS, we might risk unexpected and undesirable access paths. A caveat is added that, under v7.23, some customers have experienced benefits from an UPDATE STATISTICS LOW, and that we might run it, but prepared to remove the statistics so derived if performance nose-dives. Well, sounds like bollocks to me, but does anyone else have any views or, better still, experience of this software packeage running with Informix? Thanks Neil