Logo field has this definition:
logo:
type: array
label: Logo text and title
And is used like that in template:
<div class="fr-header__logo">
<a href="/" title="{{ 'Homepage'|t }}">
<p class="fr-logo"{% if logo.title %} title="{{ logo.title }}"{% endif %}>
{% if logo.text %}
{{ logo.text }}
{% else %}
République
<br>
Française
{% endif %}
</p>
</a>
</div>
logo.text is a slot (free renderable content) while logo.title is a string prop.
2 different things merged into a single field, this is too opaque, and will cause issue in site building (data mapping to arrays is complicated and error prone)
Split logo between logo_text field and logo_title setting.
Yes, this issue is a compatibility breaker.
Fixed
1.0
Code