I think that wether HRE is imported from CK3 to EU4 as a shattered EU-4 style HRE or as a fully centralised nation, and how close HRE is to full centralisation in the moment of conversion should depend on the crown authority which the emperor of HRE has in the moment of conversation.
For example:
If the emperor of HRE has crown authority at level 1 in CK3, HRE will transefered as fully shattered mess without any imperial reforms done as it is in vanilla EU4 at the game start.
If the emperor of HRE has crown authority at level 2 in CK3, HRE will still be shattered mess as it is in vanilla EU4 at the game start, but all imperial reforms up to Ewiger Landfriede ( forbids wars between HRE members ) will be done at EU4 game start.
If the emperor of HRE has crown authority at level 3 in CK3, HRE will still be shattered mess as it is in vanilla EU4 at the game start, but all centralisation imperial reforms up to Proclaim Erbkaisertum ( makes HRE hereditary ) will be done at EU4 game start.
If the emperor of HRE has crown authority at level 4 in CK3, HRE will appear on EU4 map as a fully centralised nation, just like all other normal EU4 nations.
P.S. Why HOI4toStellaris converter is not updated for many years?
For example:
If the emperor of HRE has crown authority at level 1 in CK3, HRE will transefered as fully shattered mess without any imperial reforms done as it is in vanilla EU4 at the game start.
If the emperor of HRE has crown authority at level 2 in CK3, HRE will still be shattered mess as it is in vanilla EU4 at the game start, but all imperial reforms up to Ewiger Landfriede ( forbids wars between HRE members ) will be done at EU4 game start.
If the emperor of HRE has crown authority at level 3 in CK3, HRE will still be shattered mess as it is in vanilla EU4 at the game start, but all centralisation imperial reforms up to Proclaim Erbkaisertum ( makes HRE hereditary ) will be done at EU4 game start.
If the emperor of HRE has crown authority at level 4 in CK3, HRE will appear on EU4 map as a fully centralised nation, just like all other normal EU4 nations.
P.S. Why HOI4toStellaris converter is not updated for many years?