immunization target rate

I remember I spot a sentence saying “for upward-slopping yield curve, immunization target return will be less than the yield to maturity rate because of lower reinvestment rate”. Why is that? If the yeild curve is upward slopping, I would assume the reinvestment rate will be higher in the future than it currently is. Any thoughts?

For upward-slopping yield curve, immunization target return will be less than the yield to maturity rate and the reinvestment rate will be higher, therefore, a lower immunization target return will be enough to meet your liability. The yield to maturity will be more than enough to meet your liability. Does it make sense ?

Correction For upward-slopping yield curve the reinvestment rate will be higher, therefore, a lower immunization target return will be enough to meet your liability. The yield to maturity will be more than enough to meet your liability. Then, immunization target return will be less than the yield to maturity rate. Does it make sense ?