This has always baffled me, never thought he was eligible and always wondered why Saliba was and this explains it now:
The case of Sarr is an interesting one. There has been some uncertainty as to whether he can be registered as a homegrown player next season, because technically when a player heads out on loan their registration at their parent club is suspended and transferred to the loan club. So under that rule, Sarr has only been registered to Tottenham for two seasons.
However, Woolwich continued to register
William Saliba on their U21 list for the Premier League throughout his three loan seasons at St Etienne, Nice and Marseille and he is now being registered by the Gunners as a homegrown player with Mikel Arteta's side heralded for finding a loophole.
A look back at the registered 2021/22 Premier League squads, while Sarr was back on loan at Metz, shows that Tottenham had also registered the Senegal international in their U21 list as Woolwich did with Saliba.
So by logic, if Woolwich can now register Saliba as homegrown then so surely can Tottenham with Sarr next season? Well, that does not appear to be the case because of some additional guidance around the homegrown rule.
That states: "A player's period on loan to a club from another National Association will not count towards the calculation of his Home Grown status unless his registration is held in suspension by the League and the FA and he continues to be entitled to be employed in the UK."
It is on the latter part where Saliba was allowed because as an EU national, he has a right to work in the UK. Sarr, born and raised in Senegal before moving to France three-and-a-half years ago in September 2020, falls outside of that remit.