You're actually overstating the Florida Republican House Speaker's claim here. He's suggested the death count may have been inflated by 10 percent, not 40 percent as you claim.
Even that is dubious, as he's relying on the same "with COVID" vs. "from COVID" misinformation as other claims questioning the death toll. "Any ‘current’ count of COVID-19 deaths is more accurately described as the number of people with COVID-19 who died, rather than those who died from COVID-19,” the Republican analysis said.
We've been over this before. Death certificates often include multiple conditions in describing the chain of events that led to death. Just look at an example death certificate from the CDC:
https://www.cdc.gov/nchs/data/dvs/blue_form.pdf
From FactCheck.org:
But the data on which all of this is based come from death certificates, which list any causes or conditions that contributed to a person’s death. In the case of COVID-19, the disease often causes other serious conditions, such as pneumonia or acute respiratory distress syndrome. Those two conditions are among the ailments with the highest counts in the CDC’s comorbidity chart. Some long-term conditions that increase the risk for severe COVID-19, such as diabetes or hypertension, were also listed.
The underlying cause of death, however, is the condition that started the chain of events that led to a person’s death. In 92% of all deaths that mention COVID-19, that disease is listed as the underlying cause of death, Jeff Lancashire, spokesman for the CDC’s National Center for Health Statistics, told FactCheck.org in an email. https://www.factcheck.org/2020/09/cdc-did-not-admit-only-6-of-recorded-deaths-from-covid-19/