The original question wasn’t answered still from my undertanding of the owners post they the owner does not want use the blade nvme drive because they dont want to replace a broken nvme which is part of the ‘fusion drive’. They want to replace a rotational HDD which was used as storage with a SSD and install and run the macOS/storage on that alone. Will it work, YES
I have a 13” Mid 2013 MacBook Air 1.7 GHz i7 with 8GB. I replaced it with a 2015 MacBook Air 1.6 GHz i5 8GB RAM logic board, it worked for the most part. The guest ID never shuts off when shutdown was activated. Also had the “not found” icon of OS folder appear on first few attempts of boot. The replacement was in error since I ordered a 1.7 GHz i7 8 GB unit but not until I did About This Mac to check memory amount did I realize I was sold and installed a 2015 i5 1.6 GHz logic board.