Offer for reduction of the repayment contribution

My parents took out one of those combination interest-only home savings/loan contracts in 2009/2010.

Recently, an "offer to reduce the repayment contribution" was made.
If I understand correctly, ignoring the offer will still result in the "choice allocation" being carried out (i.e., the home savings contract is redeemed and the loan phase begins)?

If so, a reduction would only be advantageous for the building society, as it would mean a longer interest/repayment period?

Or am I generally misunderstanding this? I must admit that I don't fully understand these binding contracts.
What is most important to me is that the loan phase "starts," so that special repayments are easily possible and at least a cost-free refinancing can take place. Provided, of course, that a correspondingly better loan contract is obtained.

Unfortunately, the offer says nothing further about the choice allocation, no date or anything else, only the offer to reduce the payment.
I would appreciate some clarity on this topic, which is quite confusing to me.

Sorry for choosing the wrong forum, hope the thread stays open and is only moved to the correct subforum

Without more information about the [Bausparvertrag] and the project, no one will really be able to help you here.

Without more information about the building savings contract and the project, no one here will really be able to help you.

The minimum savings amount was agreed at 32%, currently 44% is saved

The contracting party is Schwäbisch Hall

I am only interested in what happens if the offer is not accepted and whether my understanding of the start of the loan phase is correct, so that the building savings contract then no longer plays a role