I think its because the Alhambra has more room behind rear seats whilst the tarraco ones are more for children than full size adults and are much closer too tailgate. I currently have Alhambra as well.
Cars On Motability
2009 Citroen C4 Grand Picasso
2012 Vauxhall Antara
2013 Skoda Superb Estate
2016 Seat Alhambra
2020 Seat Tarraco
2021 Ford Kuga
2024 Nissan X-Trail left in Sep 25