Pro-rata rule ??

Every year I will contribute to my traditional IRA  and do a back-door roth IRA conversion.
For 2021, I contributed $6000 to this back-door Roth IRA.
 
1 month later, my company was acquired by another company.
And I rollover my 401K (total $112K : (i) pre-tax 401K $97K (ii) After-tax Roth $14K (iii) Pre-tax Roth $1K)  into a rollover IRA (  $97K from source[i]  ) and roth IRA (  $15K from source [ii] and [iii]  ) .
 
Today I had a chat with my company's financial advisory company, The person told me of the pro-rata rule and I may be subjected to taxation on the $6K.
 
Since it is no longer possible to revert the contribution of $6k in back-door roth ira.
I have 2 choices
[a] Pay taxes on $6k
[b] Rollover $97k into my new company's 401K plan.
 
Is what I am being told true ? Only 2 choices available ?