With person accounts enabled in an org and the default record type under Profile->Record Type Settings is set to a Person Account record type. While converting the Lead to a business account the default record type for the account isn't picked based on the default for business accounts under the selected business account record type settings.
The same is also applicable when more then one business account record type exists.
If the lead is converting to a business account and the user has more than one business record type available say Record Type 1 and Record Type 2 it will default to the business record type selected as Default under the "Default Record Type" section under Profile->Record Type Settings.
If the default is a person account record type in the record type settings then the defaulted business account record type would be based on created date. Also in such a use case, while converting a lead to person account, the record type would be picked based on overall default.
We are not using the defaults under the "Business Account and Person Account Default Record Types" section. Lead convert picks up the overall default but not the sub-default.
Please refer to Idea:- Standard and Person Account Record Type Defaults in Lead Conversion
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