Has KeyRegenerationInterval any effect in SSH2?

TL;DR: No, these options have no effect in SSH-2 (and SSH-1 support is removed since 2016).

When unsure, source code is the best documentation.

If we search for ServerKeyBits and KeyRegenerationInterval in the entire OpenSSH source code, we find only this in servconf.c:

        { "serverkeybits", sDeprecated, SSHCFG_GLOBAL },
        . . .
        { "keyregenerationinterval", sDeprecated, SSHCFG_GLOBAL },
        . . .

    case sDeprecated:
    case sIgnore:
    case sUnsupported:
        do_log2(opcode == sIgnore ?
            SYSLOG_LEVEL_DEBUG2 : SYSLOG_LEVEL_INFO,
            "%s line %d: %s option %s", filename, linenum,
            opcode == sUnsupported ? "Unsupported" : "Deprecated", arg);
        while (arg)
            arg = strdelim(&cp);
        break;

In other words, both options simply print a deprecation warning and have further no effect.

Then using the blame feature we find that the options were removed in the commit c38ea6348 of Aug 23, 2016 (OpenSSH 7.4p1):

Remove more SSH1 server code: * Drop sshd's -k option. *
Retire configuration keywords that only apply to protocol 1, as well as   the
"protocol" keyword. * Remove some related vestiges of protocol 1 support.

Before that they were used only for SSH-1. E.g. KeyRegenerationInterval:

    { "keyregenerationinterval", sKeyRegenerationTime, SSHCFG_GLOBAL },
    . . .

    case sKeyRegenerationTime:
        intptr = &options->key_regeneration_time;
        goto parse_time;

Used in sshd.c/L1442:

            if ((options.protocol & SSH_PROTO_1) &&
                key_used == 0) {
                /* Schedule server key regeneration alarm. */
                signal(SIGALRM, key_regeneration_alarm);
                alarm(options.key_regeneration_time);
                key_used = 1;
            }

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Note: for SSH-2 there's a more powerful RekeyLimit.

I'm sure that you already know this. I just didn't want to leave the question unanswered. These options (KeyRegenerationInterval & ServerKeyBits) affect the server key that is generated for SSH protocol 1. You should not have to worry about this if you demand that your connections adhere to protocol 2.