He does not count as home grown / association trained as he left the UK to join Ausburg in 2014 when he was 15 after spending early years with Reading (under 9) and MK Dons (age 9 - 14). He needed to be registered with a FA association club for 3 continuous years between the ages of 15 and 21.
UEFA rule:
An "association-trained player" is a player who, between the ages of 15 (or the start of the season during which the player turns 15) and 21 (or the end of the season during which the player turns 21), and irrespective of the player's nationality and age, has been registered with a club or with other clubs affiliated to the same association as that of the player's current club for a period, continuous or not, of three entire seasons (i.e. a period starting with the first official match of the relevant national championship and ending with the last official match of that relevant national championship) or of 36 months. In the context of this paragraph, the season immediately preceding a player’s 15th birthday may be counted if the player's birthday is after the last match of the relevant national championship but before or on 30 June (winter championships) or 31 December (summer championships), and the season immediately following the player's 21st birthday may be counted if the player's birthday is on or after 1 July (winter championships) or 1 January (summer championships) but before the first match of the relevant national championship.