There is no problem doing this without an ACR.
In answer to the original question: There is no problem as long as the batteries are roughly similar.
Good catch, miss read that.

Still, the same answer.
With or without an ACR combing batteries during charging is fine. As long as the charging voltages for each battery, and the type FLA, VRLA AGM, VRLA GEL are the same in each bank they charge without issue.
An ACR is just a machine, contactor/relay doing the same thing a human does by switching to BOTH. A VSR/ACR is just smarter than a human because it never forgets to separate the banks once they are no longer charging and always remembers to combine the for charging. Still the actual result is identical between BOTH and an ACR, they both parallel the banks...