This team is also present in Japan without a spare chassis
Williams are not the only team without a spare chassis in Japan. Alpine are also without a spare chassis if Esteban Ocon or Pierre Gasly were to damage the current chassis.
Williams have been under fire since the Australian Grand Prix because the team appeared to have no spare chassis. It cost Logan Sargeant an entry into the Australian GP after Alexander Albon damaged his chassis in FP1 and Williams decided to give the Thai the only remaining chassis after all.
Wolff takes on teams without spare chassis
Williams still has no spare chassis in Japan, but does not appear to be the only team. At the team principals' press conference, Ayao Komatsu (Haas), Bruno Famin (Alpine) and Toto Wolff (Mercedes) were asked if they do have a spare chassis. According to Komatsu, Haas have one ready, but Alpine do not: "From the next race," was Famin's answer.
Wolff, with Mercedes, logically does have a spare chassis, but stated that it is not so obvious. "Well we have a different infrastructure and resource than Williams, so we have, but I remember times even at Mercedes where it was difficult to get that third one out at the beginning of the year and then we had a season. So we were running that that risk at wale, and certainly met that at Williams, I don't think we had any spare chassis for most of the season."