Hi kearneylake,
All materials will respond to weight and will sink in more deeply under the heavier areas of the body than under the lighter areas of the body so this isn’t unique to latex. One of the advantages of latex though is that it has a higher compression modulus than other types of foam (compression modulus is the rate that a material becomes firmer with deeper compression) so it is more “supportive” than other foam materials in a similar firmness level.
Post #2 here and post #4 here also has more information about primary or “deep” support and secondary or “surface” support and their relationship to each other and to firmness and pressure relief and the “roles” of different layers in a mattress that may be helpful in clarifying how different layering combinations work better for some people and body types than for others in terms of PPP. If your mattress in its current configuration is too soft for you and your hips are sinking down too far then moving a firmer layer up (or exchanging a firmer layer for a softer one) can certainly make a difference in terms of PPP but if you purchased the Spindle mattress that you were mentioning in your previous posts then I would also make sure you talk with them so that they can also make some suggestions or provide some guidance that will be helpful as well.
Phoenix