ILR for switching category

What happens to ILR criteria is someone switches, from a Tier I entrepreneur visa ( where 5 years continous is not needed ) to Tier 2 ( where 5 years continous is needed )?

The only refusal criteria are:
convictions which had led to a sentence of imprisonment of 4 years or more; (there is no amnesty period under this sub-paragraph)
convictions which had led to a sentence of imprisonment from 12 months to under 4 years, unless 15 years have passed since the end of the sentence;
sentence to imprisonment for less than 12 months, unless 7 years have passed since the end of the sentence;
any non-custodial sentence, caution or warning within 24 months prior to the date of the decision on the application.

The time in the UK - continous residence - is the only positive criterion to be fulfilled, according to the HO.
'Continous residence' is not needed for Tier I entrepreneur.
So it is not clear what happens when someone switches from Tier I entrepreneur to Tier 2. Does the 5 year period itself start only after the switching and can it not be combined?

Grateful for expert knowledge.