I believe this is related to the updated JIS encoding (Japan Industrial Standards for encoding). Basically, when Japan wanted to enter the computer age they had to find a way to type in kanji. At that time a review of which kanji would be used in computers and how it should be written was under taken by the Japanese government. Many kanji had slight changes as the one you mentioned because there were multiple writings in use. The standard writing is probably not as is published in Heisig’s RTK as it is pre-JIS; however, both are still acceptable.