atrcts I think it depends on the level of damage you sustain during your first birth. If you have significant damage so your body is more weakened than the 'average' woman, then you might be at more risk of subsequent damage which they might not be able to repair to a certain level of acceptability.
I think when they talk about 'most damage during first vb', they are referring to what happens to an 'average' woman and how it changes her body. The first birth stretches and reshapes the body, making it more able to have another vb - hence why second vbs are 'safer' as the body doesn't have to change as much during the birth.
I think this mainly comes from information about incontinence. There is something of a myth that having a CS prevents you from becoming incontinent. Its not true, as pregnancy itself can be a cause - a CS does reduce this risk but it doesn't prevent it - and if you've already had a VB your muscles may be weaker than a woman who had a CS previously because of this. This is why there is this point about having a CS for a 2nd birth isn't necessarily going to be of benefit.
Its also about what is defined as 'normal' and 'acceptable' levels of damage to the body rather than a hard and fast rule about when most damage occurs too. A lot of damage isn't obvious or even problematic and doesn't become an issue until later in life. Once you can identify women who seems to have above average problems though, you might treat them differently than an average woman - but you can only do this after a woman has had a birth, and presented the doctors with evidence of there being an issue.
So both pieces of information - what you've been told in your particular circumstances and what Mamacici has read - would be totally true.
Most women have more damage during their first VB, but this is not prohibitive to their lives and this damage is effectively advantageous for subsequent birth. This is the average experience of women.
But in some cases a woman has had so much damage already that the risk of further damage which will cause complications and potentially will have an impact on your quality of life is significantly higher and more of a problem than the risks associated with having a CS than the average woman. This is the individual experience of a woman outside the boundaries of 'normal'.
So effectively its about balancing risk factors in individual cases and circumstances versus a generalised pattern for the overal population.
Hope that makes sense. I think if you are concerned about what you've been told, I would discuss it with your consultant about what they think your particular risks will be so you can make an informed decision, bearing in mind you are an individual and not necessarily this mythical 'average' woman.