This could be true.
In India Pixel 3aXL is priced less than Pixel 3a ( at Flipkart) this is enough evidence that 3a with its compact size is more preferred than XL sibling.
With iPhone SE2 in working, seems Google is targeting the compact mid range phones ( there are very few players in the segment of compact phones with decent specs).
With right pricing and availability, it can achieve the sucess.
But pre conditions are - enters before SE2 and Priced less than or equal to SE2.
Sorry...it seems Chinese phones will still offer better quality phones at the Pixel xa's price. 3a was sold at midrange price, but it had a rubbish chipset and cheap plastic build.