1) I've always suspected that there is an unwritten cooperation agreement between Saudi and Pakistan in defense-economic affairs. Saudi will not abandon Pakistan's economy and in return Pakistan should help shore up Saudi's core security interest. Asking for the money back in this stage is equal to abandoning Pakistan at the time of need.
2) Some Global Times articles seem to indicate that Chinese prefer Shahbaz over Imran. Chinese have the nickname 'Shahbaz speed' ? CPEC thrived under Nawaz, but has allegedly slowed under Imran. The Chinese were reportedly not happy with the establishment's move to remove Sharif family even back in 2018. Many Pakistanis here seem to think that US is the only party that prefers Sharif over Imran, but they over look the possibility that Chinese may also prefer a Sharif for Pakistan.
EDIT: The Saudi Aramco company has made a LOT of profits this year. $3 billion is nothing for the Saudi. I think they have to really have a problem with Pakistan to ask for the money back this year.