Hi eloisebig,
Thanks for your comments and feedback … I appreciate them 
Like all flexible components that are used under a mattress (such as a box spring that has springs or even an additional layer of flexible foam on the bottom of a mattress) … a flexible slat base is an “active” part of a sleeping system and can certainly make a difference for some people although it would also depend on the specifics of the mattress and on the person sleeping on it.
While I certainly wouldn’t assume that they would be helpful for everyone (and for some people or with some mattresses they can be detrimental) … there is more about the pros and cons of “active” or flexible slat support systems (either with or without the ability to change the tension/firmness in certain areas) in post #2 here and the posts it links to. They would tend to be more helpful with thinner mattresses, higher weight ranges, some types of innerspring mattresses, or for those that are more sensitive to differences in the deeper layers of a mattress or “sleeping system” and find that the additional depth of the “active” parts of their sleeping system provides a more “bottomless” and “adaptive” feel which would be a better match for them in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
Phoenix