The local Chinese paper (Lian He Zao Bao 联合早报) also features some articles about Singaporean PRs taking up citizenship. For some, they may be born in a foreign country, but they spent most of their childhood in Singapore. One story featured 22 year old Shahir Rahman who was born in Bangladesh. He migrated to Singapore with his family when he was 6 years old. His family emphasized on the importance of identity of roots, hence he was the only person in his family that took Singaporean citizenship for he identified his roots in Singapore.
There are some whose family members have settled in Singapore over the years; hence the concept of a home in Singapore is stronger, prompting them to take up citizenship in Singapore. Should we still regard new citizens as foreigners? There must be something Singapore has provided for them such that they wanted to be citizens.
You can access the article by clicking the link below. The article is in Chinese.