Aspect ratio and distorted archival footage

I saw Sing Your Song today, screened at the Vancouver International Film Centre, and I thought the filmmakers made a bizarre decision of how to treat the archival footage. Whenever the old footage was in 4:3 aspect ratio, they just stretched it horizontally to fill the screen. So in the old footage it looked like Belafonte (as well as the other actors/personalities) had a comically wide head and was squat with broad shoulders. Then they would intercut with a present-day interview of Belafonte, and of course his proportions would look normal.

Did the producers think nobody would notice? The documentary was otherwise excellent, but this issue of distortion permeated the entire length of the film; it seemed so unprofessional. Could it have somehow been an error by the theatre in how it was projected? That seems unlikely but it's just unfathomable to me that the director deliberately chose for it to look like that.