I doubt the license they have excludes ESB models as they have AT-ATs,Slave 1 and a snowspeeder which are all ESB.
The PerfectGrade falcon is in direct competition with the Revell Fine Molds kit. .
The reason I imagined the license issue is precisely because, having produced those kits, together with the Falcon in 1/144 (TFA) as well as in 1/350 (ANH), Bandai has excluded the ESB Falcon from their line as of today, which they could have easily released a variant in 1/144 or 1/350. I think there is little reason for Bandai to release the 1/350 ANH Falcon in the first place, if they were able to obtain the license to release it in the ESB version.
Also, it was when Finemolds expired their StarWars products that Bandai started selling theirs, both of which the primary market is in Japan. That is also when Revell aqired the casts of the Finemolds kits, who presumably holds the license to sell in their market (outside of Japan). Market-region-wise, the Bandai Falcon is not in competition with the Revell one, and it seems that that is how the licenses are articulated.
But the Deagostini kit is in full distribution throughout Japan, and I imagined that that could be the reason why Bandai is has/could not release ESB Falcons whether 1/350 or 1/144.
Extending my imagination, I think the most probable variant to the perfect grade Falcon would be a new trilogy Falcon, when episode IX is released and the demand reaches its full height. The engine grills of the perfect grade Falcon indicates that possibility, more so than the ESB version. If licensing is not an issue with the ESB version (or if the Deagostini kit expires in Japan by then), then Bandai might make it a convertible kit, or else the die-hard fans of the rare 5foot Falcon in ESB would be left to buy the ANH kit (for the radar dish) and the new trilogy kit, which also happens to be the most profitable path for Bandai.