Partial Roth conversion of IRA distribution

In past years my entire SEP IRA distributions have been for Roth conversions. Also until this year Schedule B has never been included in my tax return.

 

This year only part of my SEP IRA distribution was a conversion. I was prompted to enter the amount converted, which I did. I believe this is what triggered schedule B to be included as there were no other significant changes. 

 

So, my entire distribution was included on the main 1040 sheet as taxable. The converted amount was also added to part 3 of schedule B as a taxable amount.

 

What is the purpose of breaking out the conversion? I do not think I was double taxed due to breaking it out of the total distribution and adding it to schedule B. I also am aware that the IRS wants to track Roth conversions for the purpose of making sure funds have been in the roth long enough to qualify. So, why was schedule B never included in past years? 

 

In past years Turbo Tax downloaded my form 5498 which wasn't yet ready this year. 5498 has the conversion information. When TT is able to access 5498 does that preempt adding schedule B? 

Was I mistaken to file my taxes without form 5498? I assume not or TT would have prevented it knowing I made a roth conversion. Also Fidelity shows it will not be available until mid May which is past filing deadline.

 

Sorry for the long post and many questions and details. I hope they can be answered thoroughly. I didn't want to start separate threads for them.